A Gallery for City Tree Care in 2024
Planning for Trees in the City
By Len Phillips
A well-thought-out planting plan for the city forest pays off in the form of healthier trees and reduced maintenance costs. Good planning requires starting with an inventory of the existing trees and proceeds to goal setting and finally to action with a goal to plant trees everywhere possible in the city.
Street Tree Master Plan
“The Plan” is a comprehensive review that evaluates the city along with its trees and forests. The purpose of having a plan is to ensure that the city will continue to appreciate the benefits of trees through proper arboricultural management in a cost-effective manner. The Plan should briefly state what is necessary for the management of the forest and describe the measures and services required to fulfill these responsibilities to the city.
Goals
The goals of The Plan should indicate a realistic plan for achieving a 100% complete planting of trees in every available site in the city and along all the city streets. The Plan should include a planting timeline that covers a long-time span so the trees are not all the same age. The Plan should also include a species palette with recommendations for how new trees should be properly diversified by species.
The Plan should be developed by the city's arborist or a committee of interested citizens with oversight by the arborist. The arborist may need assistance from volunteers, paid staff, or consultants to gather information, conduct evaluations, and do the actual report writing. City staff members may assist the arborist depending on the workload and depending upon whether funds are available to pay for staff time assistance. Another option utilizes forestry consultants who specialize in street tree plan preparation. The Plan should contain a description of all the items listed below.
Inventory
The inventory is the counting and description of all municipal or public trees growing within a community. It should be kept up to date based on records of removals and plantings. Use the inventory to find out what you have and what you need before you choose tree species for future plantings. Make sure the inventory considers all the utilities and checks that spaces are available and suitable for replacements. The inventory can also be used to monitor the diversification of species. A good rule is to have no more than 10% of the population in one species. For design purposes, some communities may prefer one species or cultivar of a tree per block. Other communities, however, are choosing to develop a diversification program where no more than four trees of the same species or cultivar will be planted in a row.
An analysis of the inventory might include looking at needs, problems, tree values, and the comparisons between species, vigor, and location. Use the analysis to develop written goals for what the community forest should be. For example, if one of the goals is to create a forest that withstands pests and climatic extremes, plant a diverse mix of tree species. If the intention is to replace a city block with trees of the same species, that should be stated in the goals as well. In shopping areas, the merchants will have great concerns about not planting trees where they possibly may block their display windows or signs. In these situations, the arborist should consider recommending trees such as those with high canopies for stores with low signs, or low growing trees or shrubs for stores with high signs, or columnar forms in line with the edges of the building that would not block views of the windows or signs.
Where the tree population is small, the inventory could be taken every five years and not constantly kept up to date. Regardless of size, successive inventories should be compared to look for long-term trends.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Management credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
By Len Phillips
A well-thought-out planting plan for the city forest pays off in the form of healthier trees and reduced maintenance costs. Good planning requires starting with an inventory of the existing trees and proceeds to goal setting and finally to action with a goal to plant trees everywhere possible in the city.
Street Tree Master Plan
“The Plan” is a comprehensive review that evaluates the city along with its trees and forests. The purpose of having a plan is to ensure that the city will continue to appreciate the benefits of trees through proper arboricultural management in a cost-effective manner. The Plan should briefly state what is necessary for the management of the forest and describe the measures and services required to fulfill these responsibilities to the city.
Goals
The goals of The Plan should indicate a realistic plan for achieving a 100% complete planting of trees in every available site in the city and along all the city streets. The Plan should include a planting timeline that covers a long-time span so the trees are not all the same age. The Plan should also include a species palette with recommendations for how new trees should be properly diversified by species.
The Plan should be developed by the city's arborist or a committee of interested citizens with oversight by the arborist. The arborist may need assistance from volunteers, paid staff, or consultants to gather information, conduct evaluations, and do the actual report writing. City staff members may assist the arborist depending on the workload and depending upon whether funds are available to pay for staff time assistance. Another option utilizes forestry consultants who specialize in street tree plan preparation. The Plan should contain a description of all the items listed below.
Inventory
The inventory is the counting and description of all municipal or public trees growing within a community. It should be kept up to date based on records of removals and plantings. Use the inventory to find out what you have and what you need before you choose tree species for future plantings. Make sure the inventory considers all the utilities and checks that spaces are available and suitable for replacements. The inventory can also be used to monitor the diversification of species. A good rule is to have no more than 10% of the population in one species. For design purposes, some communities may prefer one species or cultivar of a tree per block. Other communities, however, are choosing to develop a diversification program where no more than four trees of the same species or cultivar will be planted in a row.
An analysis of the inventory might include looking at needs, problems, tree values, and the comparisons between species, vigor, and location. Use the analysis to develop written goals for what the community forest should be. For example, if one of the goals is to create a forest that withstands pests and climatic extremes, plant a diverse mix of tree species. If the intention is to replace a city block with trees of the same species, that should be stated in the goals as well. In shopping areas, the merchants will have great concerns about not planting trees where they possibly may block their display windows or signs. In these situations, the arborist should consider recommending trees such as those with high canopies for stores with low signs, or low growing trees or shrubs for stores with high signs, or columnar forms in line with the edges of the building that would not block views of the windows or signs.
Where the tree population is small, the inventory could be taken every five years and not constantly kept up to date. Regardless of size, successive inventories should be compared to look for long-term trends.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Management credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Tree Planting Operations
By Len Phillips
Tree List
The tree list is composed of natives, cultivars, and introductions that are tolerant of the local environment and are most suited to the specific community. In a municipal situation, the trees should not require high maintenance or be highly susceptible to pests and diseases. Additionally, no species with thorns, toxic leaves or bark, or large fruits should be used in areas of pedestrian traffic.
Tree Selection
Choose the appropriate trees for the planting site by observing the following:
Tree Size and Cost
Purchasing bigger trees is not always better. In fact, smaller stock usually outgrows and outperforms larger stock in the long-term. Smaller sizes are easier for volunteers to plant, they are cheaper for contractors or the city to purchase and plant, and they require less maintenance. For most areas, 6 – 8 feet (2 – 2½ m) Bare Root stock is a great choice. On some city streets or intensively used areas, larger specimens such as 2 – 2½ inch (5 – 6 cm) diameter stock may be necessary because it will hold up against snow plowing, wind, bicycle parking and vandalism.
Tree size can have a big impact on determining the number of trees that can be planted within the amount of available funds because smaller stock is less expensive so, more trees can be planted. For example, trees that are dug bare root are half the cost of the exact same tree Balled and Burlapped (B&B). Further, the reduced cost of shipping Bare Root (BR) trees makes the tree an even better use of limited planting funds. Vandalism or strong winds might be a reason to go with visible stakes, otherwise, plan on using root stabilization products that hold the tree roots firmly in the planting pit. The stabilizers can be purchased or made in a carpentry shop. The root stabilizer is covered with mulch and then the tree is watered as the last step in the planting process. Recent research reports have proven that selecting a smaller tree to plant at a site will increase recovery from transplant shock and grow more rapidly than planting a large tree. For example, a 1-inch (2.5 cm) diameter at breast height (dbh) tree will grow larger than a 4-inch (10 cm) tree of the same species within the first 3 years after the planting. Considering the cost, a 1-inch diameter maple tree for example, might cost less than US$100 while the same species, as a 4-inch tree might cost more than $400. That means you could purchase four small trees for the price of 1 large tree, and in 5 years, no one would know the difference because the smaller tree recovers from transplant shock more quickly. I can personally attest to the fact of seeing a smaller tree recovering from transplant shock and out growing a larger tree in three years.
Municipal Environment
The Plan should also contain an evaluation of the municipal environment, soil, climate, existing trees, land use, aesthetic character, vegetative history, etc. The evaluation should also look at the city residents, their attitude about trees and their impact on climate change, their willingness to pay for proper tree management, and their perception of the existing urban environment.
Aesthetics
Not only is the aesthetic value of a tree itself important, a tree should also be selected that is best suited for the site in terms of its aesthetic value at that site.
Nurseries
Municipal street trees can be grown in municipal nurseries or purchased from commercial nurseries, or both.
Follow-Up
At least once a year, the city should conduct a follow-up process that will evaluate the worker's performance, planting progress, trees trimmed, inventory update, etc. The process will examine the work accomplished compared to what was budgeted and this can be mentioned in an annual report.
IPM
Tree management should also look at disease and pest control through Integrated Pest Management (IPM) techniques.
Pruning
Within two years after planting, all newly planted trees should receive a structural pruning. This effort will eliminate bad growth resulting from the transplant shock recovery while also establishing the intended branch structure for the mature tree and minimizing future problems. Pruning immediately after planting was an accepted practice in the past. It was thought that fewer leaves meant less demand for water, leading to better establishment. Research by Carl Whitcomb proved that the opposite was true. Trees establish more quickly with an abundance of leaves to provide food for the regrowth of the roots left behind at the nursery.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Management credits & 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
By Len Phillips
Tree List
The tree list is composed of natives, cultivars, and introductions that are tolerant of the local environment and are most suited to the specific community. In a municipal situation, the trees should not require high maintenance or be highly susceptible to pests and diseases. Additionally, no species with thorns, toxic leaves or bark, or large fruits should be used in areas of pedestrian traffic.
Tree Selection
Choose the appropriate trees for the planting site by observing the following:
- match the USDA hardiness zone and annual rainfall of the site to the tree,
- match the tree to the size of the site,
- match the tree to the available sunlight,
- match the tree to the soils, water, and drainage requirements,
- consider potential soil compaction,
- consider the available root space,
- locate all utilities to be avoided,
- consider installing perforated pipe from the street catch basins to the street trees, so rainwater might be used to water the trees underground.
- avoid trees that might drop messy fruit, large leaves, or twigs,
- consider the budget for structural pruning of the trees,
- consider the health and type of existing plants, ordinance restrictions, and species diversity.
Tree Size and Cost
Purchasing bigger trees is not always better. In fact, smaller stock usually outgrows and outperforms larger stock in the long-term. Smaller sizes are easier for volunteers to plant, they are cheaper for contractors or the city to purchase and plant, and they require less maintenance. For most areas, 6 – 8 feet (2 – 2½ m) Bare Root stock is a great choice. On some city streets or intensively used areas, larger specimens such as 2 – 2½ inch (5 – 6 cm) diameter stock may be necessary because it will hold up against snow plowing, wind, bicycle parking and vandalism.
Tree size can have a big impact on determining the number of trees that can be planted within the amount of available funds because smaller stock is less expensive so, more trees can be planted. For example, trees that are dug bare root are half the cost of the exact same tree Balled and Burlapped (B&B). Further, the reduced cost of shipping Bare Root (BR) trees makes the tree an even better use of limited planting funds. Vandalism or strong winds might be a reason to go with visible stakes, otherwise, plan on using root stabilization products that hold the tree roots firmly in the planting pit. The stabilizers can be purchased or made in a carpentry shop. The root stabilizer is covered with mulch and then the tree is watered as the last step in the planting process. Recent research reports have proven that selecting a smaller tree to plant at a site will increase recovery from transplant shock and grow more rapidly than planting a large tree. For example, a 1-inch (2.5 cm) diameter at breast height (dbh) tree will grow larger than a 4-inch (10 cm) tree of the same species within the first 3 years after the planting. Considering the cost, a 1-inch diameter maple tree for example, might cost less than US$100 while the same species, as a 4-inch tree might cost more than $400. That means you could purchase four small trees for the price of 1 large tree, and in 5 years, no one would know the difference because the smaller tree recovers from transplant shock more quickly. I can personally attest to the fact of seeing a smaller tree recovering from transplant shock and out growing a larger tree in three years.
Municipal Environment
The Plan should also contain an evaluation of the municipal environment, soil, climate, existing trees, land use, aesthetic character, vegetative history, etc. The evaluation should also look at the city residents, their attitude about trees and their impact on climate change, their willingness to pay for proper tree management, and their perception of the existing urban environment.
Aesthetics
Not only is the aesthetic value of a tree itself important, a tree should also be selected that is best suited for the site in terms of its aesthetic value at that site.
Nurseries
Municipal street trees can be grown in municipal nurseries or purchased from commercial nurseries, or both.
Follow-Up
At least once a year, the city should conduct a follow-up process that will evaluate the worker's performance, planting progress, trees trimmed, inventory update, etc. The process will examine the work accomplished compared to what was budgeted and this can be mentioned in an annual report.
IPM
Tree management should also look at disease and pest control through Integrated Pest Management (IPM) techniques.
Pruning
Within two years after planting, all newly planted trees should receive a structural pruning. This effort will eliminate bad growth resulting from the transplant shock recovery while also establishing the intended branch structure for the mature tree and minimizing future problems. Pruning immediately after planting was an accepted practice in the past. It was thought that fewer leaves meant less demand for water, leading to better establishment. Research by Carl Whitcomb proved that the opposite was true. Trees establish more quickly with an abundance of leaves to provide food for the regrowth of the roots left behind at the nursery.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Management credits & 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Planting Bare Root Trees
By Len Phillips
When you go to the nursery to purchase a tree, bare root (BR) trees are about as basic as a tree can be. They are affordable and simple to handle, and a BR tree has a root spread twice the diameter of the same tree with its cut-off roots and soil wrapped in a burlap bag. It has also been demonstrated that a BR tree, once planted at a new location, will establish and grow at double the rate of a balled and burlapped (B&B) or containerzed tree right next to it. This can be accomplished if the bare roots have been kept moist at all times from the moment it was dug at the nursery until it was planted in its new home, and as early in the spring as possible. This applies to professional tree planting contractors, municipal employees, as well as to homeowners.
I like to tell all the contractors who are planting BR trees that “every thirty seconds that the roots are exposed to sun and wind, cuts the transplant recovery and life expectancy in half.” They get the message and while the hole is being dug, they keep the tree roots always in the shade and soaking wet. If the fine hair roots become dried out, they die and the tree will need a full growing season to replace them before normal growth can continue. If the roots have not been exposed to sunlight or drying, they will continue growing as if they were still in their original location.
I reviewed the cost of trees at major nurseries, comparing the prices between the purchase of a BR tree and the same size and species of a B&B tree. The BR tree is half the cost of the B&B tree. In addition, because they are so much lighter in weight and smaller in size, many more BR trees can fit on the bed of a truck, so they are much less expensive to ship.
A few years ago, I sent out a bid to plant trees in my city. The prices that came back were $10 to plant a BR tree and $60 to plant the same size and species B&B tree. Planting BR trees by contract is also less expensive because there is less labor required. A young tree without soil weighs little, so it is easy for a 2-person crew to dig a shallow hole and plant this tree in half an hour. The planting costs for BR trees are virtually nothing when done by trained volunteers with shovels. Planting trees with volunteers is an excellent way to plant many more trees within the budget while also letting people feel a part of a global warming solution. Many cities have an agreeable population who, with professional supervision, want to plant the trees themselves.
Bare root trees are less tolerant of the environment than larger nursery stock, particularly in the time between being dug out of the ground and planted in their new site. A nursery spokesperson told me that you can plant three BR trees for the same cost as one B&B but set aside 10% for some replacements next year unless you are a fanatic about keeping the bare roots wet at all times prior to the planting. It is the tiny root hairs that are susceptible to death by the sun or a dry wind. And it is these tiny root hairs that are what every tree needs to become established in its new home quickly. The more tiny root hairs, the more quickly the tree begins to grow in its new location.
One other major consideration when selecting a new tree is the tree size and growth rate. B&B trees take at least a full season for the roots to recover from transplant shock and another year to start to grow. This is because so many roots were chopped off at the nursery during the digging process and when the tree was planted, there is often a problem of compatibility between the soil in the root ball and the soil at the planting site. This often results in the tree taking a lot of time to recover because the roots do not seem to easily grow from one soil type to a different soil type. The BR tree has no soil with it, so it immediately adapts to the soil at its new home. However the fine root hairs on a bare root tree can easily dry out and die unless special care is provided. These root hairs do survive in a B&B rootball, but far fewer roots came from the nursery. The solution to this problem is to keep the bare tree roots wet as much as possible while in storage and especially during the planting process. The earlier in the planting season, the better for a BR tree to recover and begin to grow.
From my personal experience, I witnessed a bare root maple with a one inch trunk diameter planted right next to a four inch B&B maple of the same species planted the previous year. Four years later the BR tree had grown larger than the four inch B&B tree. Neither tree had any special treatment. However, replicating this growth is highly dependent on the soil, the handling, the water, the climate, and the species.
The following is a list of trees that tolerate being planted bare root:
Acer species, Aesculus species, Amelanchier canadensis, Amelanchier grandiflora,Carpinus betulus,
Carpinus caroliniana, Catalpa speciosa, Cercidiphyllum japonicum, Cercis canadensis, Cercis texensis, Chionanthus virginicus, Cladrastis kentukea,Corylus colurna, Crataegus species, Elaeagnus angustifolia, Eucommia ulmoides, Fraxinus species, Ginkgo species, Gleditsia species, Gymnocladus dioicus, Halesia carolina, Maackia amurensis, Malus species, Metasequoia glyptostroboides, Ostrya virginiana, Platanus × acerifolia, Populus cultivars, Prunus species, Pyrus calleryana, Robinia pseudoacacia, Salix hybrids,
Sorbus aucuparia, Syringa species, Taxodium distichum, Tilia species, Ulmus species, Zelkova serrata.
Once you have established a good practice and high survival rates with bare root plantings, you could expand your plant list to include the more challenging Betula, Celtis, Cornus, Liriodendron, Maclura, Oxydendrum, Quercus, and Styrax bare root trees. These trees need a special treatment called “sweating” before they will begin to grow.
To summarize, do everything correctly, using your best professional skills...plant into the finest soil possible and at a well-prepared site. Then plant early and handle the trees quickly. Finally, irrigate regularly until the tree is established.
Sources
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Management credits & 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
By Len Phillips
When you go to the nursery to purchase a tree, bare root (BR) trees are about as basic as a tree can be. They are affordable and simple to handle, and a BR tree has a root spread twice the diameter of the same tree with its cut-off roots and soil wrapped in a burlap bag. It has also been demonstrated that a BR tree, once planted at a new location, will establish and grow at double the rate of a balled and burlapped (B&B) or containerzed tree right next to it. This can be accomplished if the bare roots have been kept moist at all times from the moment it was dug at the nursery until it was planted in its new home, and as early in the spring as possible. This applies to professional tree planting contractors, municipal employees, as well as to homeowners.
I like to tell all the contractors who are planting BR trees that “every thirty seconds that the roots are exposed to sun and wind, cuts the transplant recovery and life expectancy in half.” They get the message and while the hole is being dug, they keep the tree roots always in the shade and soaking wet. If the fine hair roots become dried out, they die and the tree will need a full growing season to replace them before normal growth can continue. If the roots have not been exposed to sunlight or drying, they will continue growing as if they were still in their original location.
I reviewed the cost of trees at major nurseries, comparing the prices between the purchase of a BR tree and the same size and species of a B&B tree. The BR tree is half the cost of the B&B tree. In addition, because they are so much lighter in weight and smaller in size, many more BR trees can fit on the bed of a truck, so they are much less expensive to ship.
A few years ago, I sent out a bid to plant trees in my city. The prices that came back were $10 to plant a BR tree and $60 to plant the same size and species B&B tree. Planting BR trees by contract is also less expensive because there is less labor required. A young tree without soil weighs little, so it is easy for a 2-person crew to dig a shallow hole and plant this tree in half an hour. The planting costs for BR trees are virtually nothing when done by trained volunteers with shovels. Planting trees with volunteers is an excellent way to plant many more trees within the budget while also letting people feel a part of a global warming solution. Many cities have an agreeable population who, with professional supervision, want to plant the trees themselves.
Bare root trees are less tolerant of the environment than larger nursery stock, particularly in the time between being dug out of the ground and planted in their new site. A nursery spokesperson told me that you can plant three BR trees for the same cost as one B&B but set aside 10% for some replacements next year unless you are a fanatic about keeping the bare roots wet at all times prior to the planting. It is the tiny root hairs that are susceptible to death by the sun or a dry wind. And it is these tiny root hairs that are what every tree needs to become established in its new home quickly. The more tiny root hairs, the more quickly the tree begins to grow in its new location.
One other major consideration when selecting a new tree is the tree size and growth rate. B&B trees take at least a full season for the roots to recover from transplant shock and another year to start to grow. This is because so many roots were chopped off at the nursery during the digging process and when the tree was planted, there is often a problem of compatibility between the soil in the root ball and the soil at the planting site. This often results in the tree taking a lot of time to recover because the roots do not seem to easily grow from one soil type to a different soil type. The BR tree has no soil with it, so it immediately adapts to the soil at its new home. However the fine root hairs on a bare root tree can easily dry out and die unless special care is provided. These root hairs do survive in a B&B rootball, but far fewer roots came from the nursery. The solution to this problem is to keep the bare tree roots wet as much as possible while in storage and especially during the planting process. The earlier in the planting season, the better for a BR tree to recover and begin to grow.
From my personal experience, I witnessed a bare root maple with a one inch trunk diameter planted right next to a four inch B&B maple of the same species planted the previous year. Four years later the BR tree had grown larger than the four inch B&B tree. Neither tree had any special treatment. However, replicating this growth is highly dependent on the soil, the handling, the water, the climate, and the species.
The following is a list of trees that tolerate being planted bare root:
Acer species, Aesculus species, Amelanchier canadensis, Amelanchier grandiflora,Carpinus betulus,
Carpinus caroliniana, Catalpa speciosa, Cercidiphyllum japonicum, Cercis canadensis, Cercis texensis, Chionanthus virginicus, Cladrastis kentukea,Corylus colurna, Crataegus species, Elaeagnus angustifolia, Eucommia ulmoides, Fraxinus species, Ginkgo species, Gleditsia species, Gymnocladus dioicus, Halesia carolina, Maackia amurensis, Malus species, Metasequoia glyptostroboides, Ostrya virginiana, Platanus × acerifolia, Populus cultivars, Prunus species, Pyrus calleryana, Robinia pseudoacacia, Salix hybrids,
Sorbus aucuparia, Syringa species, Taxodium distichum, Tilia species, Ulmus species, Zelkova serrata.
Once you have established a good practice and high survival rates with bare root plantings, you could expand your plant list to include the more challenging Betula, Celtis, Cornus, Liriodendron, Maclura, Oxydendrum, Quercus, and Styrax bare root trees. These trees need a special treatment called “sweating” before they will begin to grow.
To summarize, do everything correctly, using your best professional skills...plant into the finest soil possible and at a well-prepared site. Then plant early and handle the trees quickly. Finally, irrigate regularly until the tree is established.
Sources
- Special thanks to Keith Warren, retired from J. Frank Schmidt & Son Co.
- J. Frank Schmidt & Son Co. 2020-2021 Price Guide
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Management credits & 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Tree Stabilizing
By Len Phillips
Guy wires and above-ground tree stakes are no longer considered appropriate for stabilizing a newly planted tree. Recent research has indicated that staking a tree from the first branch to the ground causes more harm to the tree than using root stabilizers. After guying, too many trees have been neglected, have broken tops, or are not stable when the guys are removed. There are other times when trees have become girdled because the wires were left on for too long or were too tight around the stem, killing the tree above the guy. When planting a bare root (BR) tree there was a concern that the lack of weight on the root ball might cause a bare root tree to blow over or be knocked down. This resulted in a preference for balled and burlapped (B&B) or containerized trees instead of the better choice of a BR tree.
The recommendation for staking trees has changed as the result of recent studies that showed the effect of wind sway on trees resulting in the tree developing a flare at the tie instead of at ground level where the flare should be. In addition, the staked trees created a weak spot at the tie that researchers discovered caused the tree to break off at that point of weakness. Another reason for this practice was nursery-grown trees with a trunk diameter of 1 to 2 inches (2.5 to 5 cm.), which have a relatively limited root-spread, were vulnerable to wind-throw or vandalism when they were planted in cultivated soil. Staked trees also required someone to come back in 6 to 12 months to remove the stakes, if they remember and if they were getting paid. This practice that was once thought to discourage vandalism and support the tree is NOT the best solution.
Root Stabilization
Something better to stabilize the tree was needed and researchers began to study root stabilization. This is basically a method by which the roots of a tree are firmly attached to the bottom of the planting pit with a device that is planted at the end of the planting process. The device is planted in a manner which prevents the tree roots from moving and the tree flare is allowed to develop in a normal manner at the finished grade.
There are now several root stabilizing options such as a tree staple or straps that are driven through the root system and into the soil below the tree. If you are into planting bare root trees (which you should consider since they cost half the price of B&B) any root stabilizer is perfect for holding the roots firmly in the backfill and to the bottom of the planting pit.
Change Details and Specifications
Researchers are now recommending that arborists and landscape architects change their details and specifications to illustrate planting root stabilizers below the finished grade to anchor the root ball firmly to the soil. These systems are the better option for the tree's recovery after the transplanting. They allow the tree to develop a strong natural taper up from the flare. Below-grade stabilization also meets all the safety, aesthetics and “what’s best for the tree” concerns. The big plus is that removal after the tree has become established is optional. The researchers went on to evaluate all of the known root stabilizing systems at the time of the start of the research. The evaluations were an unbiased report of their ability to stabilize a newly planted tree. The following text is an evaluation of the stabilizers and a statement of the researcher's comments. It is not intended to indicate the preference of one product as being any better than the others.
Tree Staple™
The Tree Staple™ is a below-grade stabilizer that consists of an inverted “U” shaped metal stake with a long prong that provides vertical support and serves as an anchor to the firm soil below the root ball. The shorter prong anchors the root ball and firmly locks the root ball in-place to the soil below and around the root ball. The cross member between the prongs stretches across a portion of the root ball applying downward pressure on the roots. This below-grade stabilizing system is simple and inexpensive to install. One person using a hammer can install the one, two, or three staples, as necessary, in less than a minute for each staple. No adjusting, no removal, and no dangerous stakes or wires are required. The finished product looks better than all the other stake and wire systems.
A Simple Wood Staple
A homemade root staple from 2 x 2 lumber with one long piece crossing over the root ball and screwed or nailed to two shorter pieces that are driven into solid ground on either side of the planting pit. They look like a wood staple and a pair of these staples are to be driven into opposite sides of the tree trunk so the roots are firmly held at the bottom of the planting pit. There is no need to remove this wood system after the tree is established because the wood will rot away. It could be removed a year later for possible recycling to another tree. This system is also one of the least expensive to make and install.
Other Commercial Stabilizers
Researchers have evaluated the following commercially available products that meet the requirement of anchoring the root ball firmly to the soil at the bottom of the planting pit. They are okay but are not as acceptable as the above.
Tomahawk Tree Stabilization
The Tomahawk tree stabilizer system is similar to the Tree Staple except the horizontal bar extends beyond the prongs and the prongs are hollow tubes to permit watering and fertilizing directly near the roots as needed, through the metal tubes. The horizontal bars are also notched to permit extra conventional guying to the tree trunk in extremely windy sites. Observing a video of the planting, it appears that the total time for driving a Tomahawk into the root ball requires about a minute with a hammer. The extra stabilizing requires additional time.
UPI Manufacturing Tree Stabilizer Kits
The UPI stabilizer kit comes packaged with all the components necessary to stabilize the root ball on very windy sites. These kits fit any size caliper tree and come with instructions and three 1½ in x 20 in (4x50 cm) perforated tubes. The kit also includes three 2-year time release fertilizer tablets, a 6 feet (2 meters) long harness strap, as well as cam buckles and hooks that are used to connect the harness to the tubes. The perforated tubes are planted by inserting a steel rod inside each tube and driving the rod and tube 20 inches (50 cm) into the ground just beyond the root ball. Then the steel rod is removed while leaving the hollow tube in the ground and the process is repeated until all three tubes are in the ground at an equal distance around the root ball. When the tubes are in the ground the tree is planted and harness straps are planted between the tubes and over the root system. Once established (or after 8 to 12 months), the harness straps may be removed for use elsewhere while the tubes remain in the ground and continue to provide a simple way to provide water, oxygen, and dissolved fertilizer to the roots for years to come. This product planting requires two people about 20 minutes to plant.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Science credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Municipal Tree Management Operations
By Len Phillips
Urban Forestry Department – The Plan
To begin an analysis of a city's Urban Forestry Department or a large parcel of land, a study called “The Plan” should be made of the following items: the planting program, the number of trees to be maintained; frequency of the trimming cycle; workload per year; equipment and personnel required; a budget; support services and contracts; employee training and morale; and other related items unique to each community. The study should include the municipal forestry management program and a comparison made with the industry, the standards, and the practices in other communities. The Plan should also identify economical work methods and procedures that will enhance existing operations. Careful planning through The Plan will improve the cost-effectiveness of the operations.
Equipment
A general knowledge of the basic and most efficient tools is essential for efficient street tree management. Tree pruning is the costliest operation in urban forestry budgets. Besides structural pruning six to eighteen months after planting, scheduled pruning and mechanization will reduce the costs for the benefit of the entire department. Replacement equipment should consider going “green”. For example, switching to battery-powered chainsaws should be a top priority.
Contracting
Contracting, versus using in-house labor, versus some of both, should be studied and prices compared in order to ensure that quality tree maintenance is being performed at the lowest possible cost. Some smaller cities require all bidders for tree trimming contracts to be TCIA-accredited tree care companies. The price might be a bit higher, but municipal supervision will be minimal or unnecessary because these accredited company employees are so highly trained in proper tree care that local supervision only needs to be casual.
Regulations
The municipal regulations pertaining to tree plantings, tree management, and tree removals as well as other local and state regulations pertaining to street trees should be evaluated and made a part of The Plan.
Operations and Maintenance Plan
One of the key elements to efficient operations is the development of a long-term implementation strategy that includes annual goals that the forestry department intends to implement. The budget and funding section should be individualized according to the local community requests, and it should provide details that will meet the needs of the community's urban forest sustainability as well as the practical limitations of municipal funding. The budget section should not only include cost estimates to implement each section of the plan, but it should also indicate funding sources including grants that might be used to offset the local government costs.
The Plan should require the pruning cycle for trimming street trees to be systematic, as opposed to trimming on demand. The pruning cycle will decrease the cost per tree while increasing the safety and condition of the trees and reducing demand and storm damage requests. This effort also results in a better public image.
Public Relations
Public support comes in the form of the public's perception regarding the Urban Forestry program. The staff should be willing to meet with the public whenever the opportunity presents itself. When a tree planting program is being planned, the arborist should meet with the homeowners to obtain their thoughts on the tree to be selected for in front of their home. The arborist should offer residents a choice of trees if possible and make suggestions for its proper location.
Often residents may come out and want to talk to the pruning crew, who should take the time to discuss what is being done and why. Public support is necessary in order to obtain the funding necessary to pay for street tree management. Public support can be enhanced through a wide variety of public relations programs. In addition to communication with residents during tree planting and pruning, some of the best PR programs are described below.
Arbor Day
Arbor Day is the day to celebrate trees. Everyone involved in arboriculture should take advantage of, observe, and celebrate this holiday. When applicable, the Tree City USA award should be announced. In addition, as a tree is being planted, the arborist should be indicating to the audience the latest tree planting techniques, such as bare root planting, or removing the burlap, and root stabilization instead of staking, etc.
Tree City USA
This program, sponsored by the National Arbor Day Foundation, is a very popular program that draws attention to a city's urban forestry program. Tree City USA is awarded to communities that meet four requirements:
1. it must have a tree board or tree department;
2. it must have a tree ordinance or by-law;
3. it must have a comprehensive urban forestry program supported by a minimum of two dollars per capita;
4. it must make an Arbor Day proclamation and hold a commemorative tree planting at a public ceremony. The arborist should be in charge of this event and use the tree planting to illustrate proper tree care and
encourage the residents to grow trees in their yards.
Tree Advisory Board
All public support must be channeled through a street tree advisory board. This is a group of volunteers chosen by the mayor. Their task is to establish the policies and recommendations that the Urban Forestry Department must follow.
Volunteers
Volunteers can also be used to assist in other aspects of the urban forestry program, especially for tree planting projects. The volunteers should receive training in proper tree planting and tree care. Many cities also have citizen pruning organizations that provide training in proper pruning and tools to structurally prune small and recently planted trees. Any city that has a program for volunteers must also be sure to have a “Volunteer Appreciation Day”.
Sources
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Management credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
By Len Phillips
Urban Forestry Department – The Plan
To begin an analysis of a city's Urban Forestry Department or a large parcel of land, a study called “The Plan” should be made of the following items: the planting program, the number of trees to be maintained; frequency of the trimming cycle; workload per year; equipment and personnel required; a budget; support services and contracts; employee training and morale; and other related items unique to each community. The study should include the municipal forestry management program and a comparison made with the industry, the standards, and the practices in other communities. The Plan should also identify economical work methods and procedures that will enhance existing operations. Careful planning through The Plan will improve the cost-effectiveness of the operations.
Equipment
A general knowledge of the basic and most efficient tools is essential for efficient street tree management. Tree pruning is the costliest operation in urban forestry budgets. Besides structural pruning six to eighteen months after planting, scheduled pruning and mechanization will reduce the costs for the benefit of the entire department. Replacement equipment should consider going “green”. For example, switching to battery-powered chainsaws should be a top priority.
Contracting
Contracting, versus using in-house labor, versus some of both, should be studied and prices compared in order to ensure that quality tree maintenance is being performed at the lowest possible cost. Some smaller cities require all bidders for tree trimming contracts to be TCIA-accredited tree care companies. The price might be a bit higher, but municipal supervision will be minimal or unnecessary because these accredited company employees are so highly trained in proper tree care that local supervision only needs to be casual.
Regulations
The municipal regulations pertaining to tree plantings, tree management, and tree removals as well as other local and state regulations pertaining to street trees should be evaluated and made a part of The Plan.
Operations and Maintenance Plan
One of the key elements to efficient operations is the development of a long-term implementation strategy that includes annual goals that the forestry department intends to implement. The budget and funding section should be individualized according to the local community requests, and it should provide details that will meet the needs of the community's urban forest sustainability as well as the practical limitations of municipal funding. The budget section should not only include cost estimates to implement each section of the plan, but it should also indicate funding sources including grants that might be used to offset the local government costs.
The Plan should require the pruning cycle for trimming street trees to be systematic, as opposed to trimming on demand. The pruning cycle will decrease the cost per tree while increasing the safety and condition of the trees and reducing demand and storm damage requests. This effort also results in a better public image.
Public Relations
Public support comes in the form of the public's perception regarding the Urban Forestry program. The staff should be willing to meet with the public whenever the opportunity presents itself. When a tree planting program is being planned, the arborist should meet with the homeowners to obtain their thoughts on the tree to be selected for in front of their home. The arborist should offer residents a choice of trees if possible and make suggestions for its proper location.
Often residents may come out and want to talk to the pruning crew, who should take the time to discuss what is being done and why. Public support is necessary in order to obtain the funding necessary to pay for street tree management. Public support can be enhanced through a wide variety of public relations programs. In addition to communication with residents during tree planting and pruning, some of the best PR programs are described below.
Arbor Day
Arbor Day is the day to celebrate trees. Everyone involved in arboriculture should take advantage of, observe, and celebrate this holiday. When applicable, the Tree City USA award should be announced. In addition, as a tree is being planted, the arborist should be indicating to the audience the latest tree planting techniques, such as bare root planting, or removing the burlap, and root stabilization instead of staking, etc.
Tree City USA
This program, sponsored by the National Arbor Day Foundation, is a very popular program that draws attention to a city's urban forestry program. Tree City USA is awarded to communities that meet four requirements:
1. it must have a tree board or tree department;
2. it must have a tree ordinance or by-law;
3. it must have a comprehensive urban forestry program supported by a minimum of two dollars per capita;
4. it must make an Arbor Day proclamation and hold a commemorative tree planting at a public ceremony. The arborist should be in charge of this event and use the tree planting to illustrate proper tree care and
encourage the residents to grow trees in their yards.
Tree Advisory Board
All public support must be channeled through a street tree advisory board. This is a group of volunteers chosen by the mayor. Their task is to establish the policies and recommendations that the Urban Forestry Department must follow.
Volunteers
Volunteers can also be used to assist in other aspects of the urban forestry program, especially for tree planting projects. The volunteers should receive training in proper tree planting and tree care. Many cities also have citizen pruning organizations that provide training in proper pruning and tools to structurally prune small and recently planted trees. Any city that has a program for volunteers must also be sure to have a “Volunteer Appreciation Day”.
Sources
- Dodge, Linda, "Current Research", Pacific Northwest Trees, Spring 2001
- Gilman, Edward F., "Planting trees in landscapes", Environmental Horticulture Department, IFAS, University of Florida, 2004
- Hagen, Bruce, "The Ecology of Urban Trees", City Trees, The Journal of The Society of Municipal Arborists Vol. 37, Number 5, September/October 2001
- "Knoxville Street Tree Master Plan", Knoxville-Knox County Metropolitan Planning Commission, 2002
- Phillips, Leonard, "Municipal Street Tree Master Plan", City Trees, The Journal of The Society of Municipal Arborists Vol. 30, Number 3, May/June 1994
- Phillips, Leonard, “Urban Trees”, McGraw-Hill, 1993.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Management credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Watering Trees after Planting
Edited by Len Phillips
The most neglected part of the planting process is an extended commitment to watering during the critical months following a tree planting. Part of the problem lies in the fact that specific recommendations about frequency and amount of water to apply are almost impossible to give, especially on sites where soils have been altered. The arborist overseeing the planting program must adapt the watering recommendations to match the different species and the different soils.
Water acts as a coolant, keeping the tree from overheating on hot summer days. It is also essential for the tree to manufacture the food it needs to grow. Water serves as a system for transporting nutrients from the soil to the leaves and for the manufactured food that then moves throughout the tree. The lack of available water reduces the tree’s ability to make food and maintain normal functions. Symptoms of water stress include wilting and loss of leaves. A tree also “screams” in distress when air bubbles have replaced water moving up the tree.
Removing branches during the planting process for compensatory pruning to make up for lost roots, was a common practice in the past. It was thought that fewer leaves meant less demand for water, leading to better establishment. Research by Carl Whitcomb and others proved that just the opposite was true. Trees establish more quickly with abundant leaves to provide food for the regrowth of the roots left behind at the nursery.
Watering New Trees
When a tree is planted, the planting hole should be filled with water after the hole is dug but before the tree is planted, then filled again after the tree has been planted. The planting site should be filled two more times within 24 hours after planting. Even if it is raining, a thorough watering will eliminate trapped air pockets and reduce transplant shock. This is especially true for bare root trees. The fine roots and root hairs need to be surrounded with soil to minimize transplant shock. After planting, a thorough watering once a week is necessary until the end of the growing season. On extremely hot or windy days, a very fine misting of the leaves may be necessary several times a day. Watering may also be necessary during drought periods for a few years after planting. Mulching trees with a 1 – 3 inch (2.5 – 8 cm) thick layer of woodchips or other mulch is recommended as it helps reduce evaporation and conserves the water in the soil.
Frequently irrigated trees and shrubs establish faster than those receiving infrequent irrigation. This seems especially true for container-grown nursery stock. Initially, the best place to check water needs is in the root ball or soils in direct contact with the roots. Moisture in these relatively small areas will be the water source for the tree until the root system grows into or through the backfill.
Recent evidence suggests that a heavy watering is essential as part of the planting process, but frequent irrigation after planting provides more benefit than applying large volumes of water infrequently during the period when the roots are becoming established. Within two to three days, root balls of newly planted trees will dry to levels that impede root growth. Be sure to gradually increase the area irrigated around the tree to accommodate root growth.
For trees planted in spring or summer, provide water one to three times a week during the first few months after planting. Daily irrigation in the warmer weather provides the quickest establishment. Following the initial few months of frequent irrigation, begin to provide weekly irrigation until trees are fully established. In most landscapes that receive more than 30 inches (80 cm) of rain annually, if the mulch area is maintained weed-free, irrigation does not need to be applied outside of the root ball. Never add water if the root ball is saturated.
The maximum size tree of the tree should be determined not only by the budget, but also by irrigation capabilities and climate. If irrigation cannot be provided, choose smaller nursery stock to ensure survival. If trees are irrigated infrequently, only seeds, seedlings, or small saplings of drought tolerant trees should be planted. Small-sized nursery stock and bare root trees have a small crown, so roots come into balance with the leaves soon after planting. Once roots come into balance with the top of the tree, they usually grow well with rainfall alone. If trees will be irrigated only until they are established, drought tolerant trees should be chosen, and nursery stock of any size can be planted.
Roots must generate and grow into surrounding soils before a larger soil volume can be tapped for moisture. Tree roots grow approximately 18 inches (½ m) in length annually in most locations. Trees will become established within 1 – 1½ years for each caliper inch of stem. Thus, it takes 2 – 3 years before a 2 inch (5 cm) tree is established.
In climates with severe winters, it is unlikely that shallow-rooted trees would have the opportunity to replace lost moisture since the soil is frozen from early December until sometime in March. Cold hardiness research has shown slight moisture stress accelerates cold acclimation, and lower tissue water levels frequently correspond to greater low-temperature tolerance. Researchers have demonstrated plant root tissues become more resistant to water uptake and/or translocation during the onset of cold acclimation.
Watering Devices
Water can be applied by asking adjacent homeowners to keep the tree watered or send out a truck with a water tank and hose. To cut back on watering costs, many people have started using commercially manufactured watering products. The most popular product is Treegator® which is designed to hold gallons of water and release it slowly from small holes in the bottom of the bag. The TreeDiaper® and Growth Ring® products swell up with water like an old-fashioned inner tube from an automobile tire. The water in these products seeps out slowly. They can maintain relatively uniform soil moisture levels and are especially useful because the soil absorbs water very slowly. “Greenwell Water Savers” and other plastic water-holding rings are planted around the edge of the planting pit and are designed to hold several gallons of water around the tree trunk to provide a quick filling of delivered water. The water then soaks into the soil all around the newly planted tree. Water-filled “cocoon pots” work well for small stock in hard-to-access locations but are not recommended for watering public trees.
The watering frequency should be reduced and the area to be watered enlarged. Newly planted trees and shrubs should not be irrigated as frequently or with the same amount of water as newly seeded turfgrass. Trees in shady spots may not require as much water as trees in sunny areas. Automatic irrigation systems must be monitored continuously and turned off during periods of heavy rainfall. Apply water in the early morning or late evening to avoid quick evaporation that would occur during warmer daylight hours.
Many cities hire high school or college students in the summer months for the sole purpose of watering newly planted trees. Most students have a pickup truck pulling a water tank, or with the tank and hose in the bed of the truck. The truck goes to newly planted trees and fills the water bags or tree saucers. Some cities have students on bicycles pulling a water tank on a trailer hitch welded to the rear of the bike.
Many new major construction projects are calling for new sidewalks, storm drains, and trees. When this opportunity arises, the arborist should request that plant pits are a minimum of 5' x 10' and either CU Soil is utilized or soil cells be installed under the sidewalks and perforated pipes be located between the catch basins and the new trees. This allows the tree to have a large area of moist soil that will allow the tree to grow to mature size and to be watered with street runoff water every time it rains. This technique also cleans the surplus water passing through the soil, before it enters the municipal stormwater system.
Fall Watering?
To prevent or reduce the incidence of winter injury (winter browning on conifers in particular), arborists have adopted the practice of thoroughly soaking their woody plants just prior to soil freeze-up. This implies that trees will need to replace moisture lost via transpiration in winter.
But there are two problems with this long-standing recommendation:
water levels frequently correspond to greater low-temperature tolerance. Researchers have demonstrated
that plant root tissues become more resistant to water uptake and/or translocation during the onset of cold
acclimation.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Edited by Len Phillips
The most neglected part of the planting process is an extended commitment to watering during the critical months following a tree planting. Part of the problem lies in the fact that specific recommendations about frequency and amount of water to apply are almost impossible to give, especially on sites where soils have been altered. The arborist overseeing the planting program must adapt the watering recommendations to match the different species and the different soils.
Water acts as a coolant, keeping the tree from overheating on hot summer days. It is also essential for the tree to manufacture the food it needs to grow. Water serves as a system for transporting nutrients from the soil to the leaves and for the manufactured food that then moves throughout the tree. The lack of available water reduces the tree’s ability to make food and maintain normal functions. Symptoms of water stress include wilting and loss of leaves. A tree also “screams” in distress when air bubbles have replaced water moving up the tree.
Removing branches during the planting process for compensatory pruning to make up for lost roots, was a common practice in the past. It was thought that fewer leaves meant less demand for water, leading to better establishment. Research by Carl Whitcomb and others proved that just the opposite was true. Trees establish more quickly with abundant leaves to provide food for the regrowth of the roots left behind at the nursery.
Watering New Trees
When a tree is planted, the planting hole should be filled with water after the hole is dug but before the tree is planted, then filled again after the tree has been planted. The planting site should be filled two more times within 24 hours after planting. Even if it is raining, a thorough watering will eliminate trapped air pockets and reduce transplant shock. This is especially true for bare root trees. The fine roots and root hairs need to be surrounded with soil to minimize transplant shock. After planting, a thorough watering once a week is necessary until the end of the growing season. On extremely hot or windy days, a very fine misting of the leaves may be necessary several times a day. Watering may also be necessary during drought periods for a few years after planting. Mulching trees with a 1 – 3 inch (2.5 – 8 cm) thick layer of woodchips or other mulch is recommended as it helps reduce evaporation and conserves the water in the soil.
Frequently irrigated trees and shrubs establish faster than those receiving infrequent irrigation. This seems especially true for container-grown nursery stock. Initially, the best place to check water needs is in the root ball or soils in direct contact with the roots. Moisture in these relatively small areas will be the water source for the tree until the root system grows into or through the backfill.
Recent evidence suggests that a heavy watering is essential as part of the planting process, but frequent irrigation after planting provides more benefit than applying large volumes of water infrequently during the period when the roots are becoming established. Within two to three days, root balls of newly planted trees will dry to levels that impede root growth. Be sure to gradually increase the area irrigated around the tree to accommodate root growth.
For trees planted in spring or summer, provide water one to three times a week during the first few months after planting. Daily irrigation in the warmer weather provides the quickest establishment. Following the initial few months of frequent irrigation, begin to provide weekly irrigation until trees are fully established. In most landscapes that receive more than 30 inches (80 cm) of rain annually, if the mulch area is maintained weed-free, irrigation does not need to be applied outside of the root ball. Never add water if the root ball is saturated.
The maximum size tree of the tree should be determined not only by the budget, but also by irrigation capabilities and climate. If irrigation cannot be provided, choose smaller nursery stock to ensure survival. If trees are irrigated infrequently, only seeds, seedlings, or small saplings of drought tolerant trees should be planted. Small-sized nursery stock and bare root trees have a small crown, so roots come into balance with the leaves soon after planting. Once roots come into balance with the top of the tree, they usually grow well with rainfall alone. If trees will be irrigated only until they are established, drought tolerant trees should be chosen, and nursery stock of any size can be planted.
Roots must generate and grow into surrounding soils before a larger soil volume can be tapped for moisture. Tree roots grow approximately 18 inches (½ m) in length annually in most locations. Trees will become established within 1 – 1½ years for each caliper inch of stem. Thus, it takes 2 – 3 years before a 2 inch (5 cm) tree is established.
In climates with severe winters, it is unlikely that shallow-rooted trees would have the opportunity to replace lost moisture since the soil is frozen from early December until sometime in March. Cold hardiness research has shown slight moisture stress accelerates cold acclimation, and lower tissue water levels frequently correspond to greater low-temperature tolerance. Researchers have demonstrated plant root tissues become more resistant to water uptake and/or translocation during the onset of cold acclimation.
Watering Devices
Water can be applied by asking adjacent homeowners to keep the tree watered or send out a truck with a water tank and hose. To cut back on watering costs, many people have started using commercially manufactured watering products. The most popular product is Treegator® which is designed to hold gallons of water and release it slowly from small holes in the bottom of the bag. The TreeDiaper® and Growth Ring® products swell up with water like an old-fashioned inner tube from an automobile tire. The water in these products seeps out slowly. They can maintain relatively uniform soil moisture levels and are especially useful because the soil absorbs water very slowly. “Greenwell Water Savers” and other plastic water-holding rings are planted around the edge of the planting pit and are designed to hold several gallons of water around the tree trunk to provide a quick filling of delivered water. The water then soaks into the soil all around the newly planted tree. Water-filled “cocoon pots” work well for small stock in hard-to-access locations but are not recommended for watering public trees.
The watering frequency should be reduced and the area to be watered enlarged. Newly planted trees and shrubs should not be irrigated as frequently or with the same amount of water as newly seeded turfgrass. Trees in shady spots may not require as much water as trees in sunny areas. Automatic irrigation systems must be monitored continuously and turned off during periods of heavy rainfall. Apply water in the early morning or late evening to avoid quick evaporation that would occur during warmer daylight hours.
Many cities hire high school or college students in the summer months for the sole purpose of watering newly planted trees. Most students have a pickup truck pulling a water tank, or with the tank and hose in the bed of the truck. The truck goes to newly planted trees and fills the water bags or tree saucers. Some cities have students on bicycles pulling a water tank on a trailer hitch welded to the rear of the bike.
Many new major construction projects are calling for new sidewalks, storm drains, and trees. When this opportunity arises, the arborist should request that plant pits are a minimum of 5' x 10' and either CU Soil is utilized or soil cells be installed under the sidewalks and perforated pipes be located between the catch basins and the new trees. This allows the tree to have a large area of moist soil that will allow the tree to grow to mature size and to be watered with street runoff water every time it rains. This technique also cleans the surplus water passing through the soil, before it enters the municipal stormwater system.
Fall Watering?
To prevent or reduce the incidence of winter injury (winter browning on conifers in particular), arborists have adopted the practice of thoroughly soaking their woody plants just prior to soil freeze-up. This implies that trees will need to replace moisture lost via transpiration in winter.
But there are two problems with this long-standing recommendation:
- In climates with severe winters, it is unlikely that shallow-rooted trees would have the opportunity to replace lost moisture since the soil is frozen from early December until sometime in March.
water levels frequently correspond to greater low-temperature tolerance. Researchers have demonstrated
that plant root tissues become more resistant to water uptake and/or translocation during the onset of cold
acclimation.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
The Biochar Project
Edited by Len Phillips
Björn Embrén and his colleagues started helping city trees in Stockholm, Sweden, by placing rock and broken sidewalk pieces in the root zone of the trees, with a sandy loam, clay, and peat mix washed in between the rocks. The soil and rock helped the trees grow better by creating voids in the compacted soil and the ground was more able to absorb stormwater, creating an urban soil management process that became known as the “Stockholm Tree Pits”.
While Embrén was improving urban tree growth, the city’s waste department was having problems with what to do with the plant debris or green waste collected from the city’s gardens and tree trimmings from residents and City properties. After communications among the various department heads, the result was the development of The Biochar Project.
Embrén started applying biochar, a type of charcoal made from green waste, as a variant to his rock/soil mix, with dramatic results. Over the course of a two-week period, a patch of lawn had biochar mixed into the soil and the grass grew with an almost alarming speed. Valuable fungus, bacteria, and microorganisms started to flourish, creating a real concentration of organisms useful for creating healthy soil. The biochar held nutrients and moisture in the earth until the surrounding plant roots were able to take it up.
In the end, the waste department created a biochar production facility and the by-product of heat was also useful for providing warmth and hot water to nearby homes on the city's heat distribution network. Embrén got the biochar to use in his tree planting and existing tree improvement projects.
Pyrolysis
Biochar is made by pyrolysis, which is created by heating organic biomass in a low oxygen environment at very high temperatures that often reach 1,472° F (800° C ). Half of the garden waste becomes a very stable, porous, carbon-rich, durable biochar, while the other half becomes a gas that is burned to create more biochar. Adding biochar to the soil at the time of planting, or incorporating it at the base of established trees makes the soil a more desirable environment for root growth and may also alleviate some of the environmental stress experienced by city trees, such as drought, water-logging, and high levels of salinity.
The pyrolysis gas being burned to create more biochar has a surplus heat that creates steam for use by the city's heat distribution network. Using the gas this way does release some of the carbon dioxide that the plants absorbed when they were alive, but it’s far less than what would be released if the plant waste was just incinerated by conventional means or other fuels were used to provide heat. The biochar process is a carbon-neutral process, releasing no more carbon than the plants absorbed during their lifetimes.
During the trials of making biochar, the city saw spectacular results. The pilot plant burned 1,200 tons of green waste, trapping a carbon equivalent to the annual emissions of 700 cars. When this process begins to operate at full capacity, the emissions from an equivalent of 3,500 cars will be taken away from the streets and the process will supply heat and hot water for 400 apartments.
Stockholm expects much of the biochar will be used on the city's trees. However, they also plan to encourage garden owners to pick up bags of the biochar and reintroduce it into the soil of their gardens. Other final destinations include the city’s many public green areas. The demand for the biochar is expected to far exceed the actual supply. The biochar production facility could provide ultra-clean green power using the green waste products of agriculture and forestry to provide a biochar that could be plowed into fields to boost fertility.
Already the concept has spread beyond Sweden and across the Atlantic. California officials have been in touch with the Stockholm project staff and have bought the equipment necessary to make their own biochar. In a region vulnerable to droughts, Californians seem to be especially interested in biochar’s ability to lock slow-release moisture into the soil, reducing the need for irrigation.
California’s different tack shows how the combined biochar and energy production process could prove influential far beyond the confines of the Swedish capital. Stockholm biochar may be starting small by freeing the city sidewalks of sad-looking trees, but the future possibilities are so much greater.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.25 BCMA Practice & 0.25 BCMA Science credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Edited by Len Phillips
Björn Embrén and his colleagues started helping city trees in Stockholm, Sweden, by placing rock and broken sidewalk pieces in the root zone of the trees, with a sandy loam, clay, and peat mix washed in between the rocks. The soil and rock helped the trees grow better by creating voids in the compacted soil and the ground was more able to absorb stormwater, creating an urban soil management process that became known as the “Stockholm Tree Pits”.
While Embrén was improving urban tree growth, the city’s waste department was having problems with what to do with the plant debris or green waste collected from the city’s gardens and tree trimmings from residents and City properties. After communications among the various department heads, the result was the development of The Biochar Project.
Embrén started applying biochar, a type of charcoal made from green waste, as a variant to his rock/soil mix, with dramatic results. Over the course of a two-week period, a patch of lawn had biochar mixed into the soil and the grass grew with an almost alarming speed. Valuable fungus, bacteria, and microorganisms started to flourish, creating a real concentration of organisms useful for creating healthy soil. The biochar held nutrients and moisture in the earth until the surrounding plant roots were able to take it up.
In the end, the waste department created a biochar production facility and the by-product of heat was also useful for providing warmth and hot water to nearby homes on the city's heat distribution network. Embrén got the biochar to use in his tree planting and existing tree improvement projects.
Pyrolysis
Biochar is made by pyrolysis, which is created by heating organic biomass in a low oxygen environment at very high temperatures that often reach 1,472° F (800° C ). Half of the garden waste becomes a very stable, porous, carbon-rich, durable biochar, while the other half becomes a gas that is burned to create more biochar. Adding biochar to the soil at the time of planting, or incorporating it at the base of established trees makes the soil a more desirable environment for root growth and may also alleviate some of the environmental stress experienced by city trees, such as drought, water-logging, and high levels of salinity.
The pyrolysis gas being burned to create more biochar has a surplus heat that creates steam for use by the city's heat distribution network. Using the gas this way does release some of the carbon dioxide that the plants absorbed when they were alive, but it’s far less than what would be released if the plant waste was just incinerated by conventional means or other fuels were used to provide heat. The biochar process is a carbon-neutral process, releasing no more carbon than the plants absorbed during their lifetimes.
During the trials of making biochar, the city saw spectacular results. The pilot plant burned 1,200 tons of green waste, trapping a carbon equivalent to the annual emissions of 700 cars. When this process begins to operate at full capacity, the emissions from an equivalent of 3,500 cars will be taken away from the streets and the process will supply heat and hot water for 400 apartments.
Stockholm expects much of the biochar will be used on the city's trees. However, they also plan to encourage garden owners to pick up bags of the biochar and reintroduce it into the soil of their gardens. Other final destinations include the city’s many public green areas. The demand for the biochar is expected to far exceed the actual supply. The biochar production facility could provide ultra-clean green power using the green waste products of agriculture and forestry to provide a biochar that could be plowed into fields to boost fertility.
Already the concept has spread beyond Sweden and across the Atlantic. California officials have been in touch with the Stockholm project staff and have bought the equipment necessary to make their own biochar. In a region vulnerable to droughts, Californians seem to be especially interested in biochar’s ability to lock slow-release moisture into the soil, reducing the need for irrigation.
California’s different tack shows how the combined biochar and energy production process could prove influential far beyond the confines of the Swedish capital. Stockholm biochar may be starting small by freeing the city sidewalks of sad-looking trees, but the future possibilities are so much greater.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.25 BCMA Practice & 0.25 BCMA Science credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
The Best Time to Prune Trees
Edited by Len Phillips
There are lots of factors to consider before pruning. Here are several very common landscape tree species and a general breakdown of when and how to prune them that best suits their needs and avoids pest problems.
Oaks (Quercus)
Pruning young oaks is important in order to start the tree with proper structure and a well-balanced shape. As they age, pruning involves removing dead and diseased wood rather than maintaining shape. Because of disease, oak trees have a very specific window of when you should NOT prune them. Oak wilt is caused by a fungus (Ceraticystis fagacearum) that is spread by Nitidulid (sap) beetles. These beetles are most active during the spring months, generally from February through May. By not pruning oak trees during this period, sap from the pruning will not attract the insects and provide an easy access for the fungus to get inside the tree. The best time to prune oaks is November through January when the beetles are least active. If making a pruning cut during sap flow, cover the wound with a sealant like a warm wax or pitch specially made for sealing tree grafts and wounds.
Maples (Acer)
Maples are pretty forgiving and do not necessarily have any special considerations for pruning and trimming. The only exceptions are to avoid pruning maples in the early spring or when they are not healthy. Maple trees move large amounts of sap in the spring and if a cut is made during this time, the tree will bleed heavily. Later in the spring as the tree is budding and growing new leaves, they will not put as much energy into healing the wound as they put into growing their leaves, which could result in disease problems. This also applies to when maples drop their leaves in autumn. Silver maples (Acer saccharinum) grow suckers often if the tree is over pruned and those suckers can be trimmed at any time of the year.
Willow (Salix)
Willow trees, in general, are one tree that can be pruned just about anytime and anywhere. But like most trees, it’s usually best to prune when the tree is dormant in winter.
Keep in mind when pruning a willow:
Elm (Ulmus)
Elm trees need a lot of special consideration when it comes to pruning them because of Dutch elm disease (DED). The only real good time to avoid the spore causing DED from entering vulnerable wounds is in the very early spring. In fact, lots of cities have laws regarding when elms can be pruned to help contain the disease. Elm trees are pruned very similar to how other trees are pruned. Remove old, dead wood, crossing and suckering branches, and other unsightly, unbalanced growth. Good pruning at the right time can help the elm fight off DED and recover from infections.
Poplar (Populus)
Poplar trees are best pruned when they are entering dormancy in the late summer and autumn. This time is also good because they will not put forth the energy to grow suckers. When pruning poplars, take great care to approach cuts with an “easy-does-it” attitude. Avoid tearing bark. To prune poplar correctly, cut the weight off of the branch gradually before making the final cut. Regular pruning of these fast-growing trees will extend their life and create a nice looking mature specimen.
Conifers
Conifers are generally trees that do not require a lot of pruning or trimming, and do not recover well after pruning. The two main reasons to prune a conifer are for health (removing of old, dead, diseased growth) and for size control (which is avoidable by planting a conifer at a place that is the right size for the mature tree).
When and how a conifer is pruned depends on the species.
Hardwood Trees and Shrubs Without Showy Flowers
Prune these trees in the dormant season to:
Flowering Trees and Shrubs
These can be pruned during the dormant season for the same reasons stated above. However, to preserve the current year's flower crop, prune according to the following schedule:
Source
"All Things Trees blog”, American Tree Service Supply, 2013.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Edited by Len Phillips
There are lots of factors to consider before pruning. Here are several very common landscape tree species and a general breakdown of when and how to prune them that best suits their needs and avoids pest problems.
Oaks (Quercus)
Pruning young oaks is important in order to start the tree with proper structure and a well-balanced shape. As they age, pruning involves removing dead and diseased wood rather than maintaining shape. Because of disease, oak trees have a very specific window of when you should NOT prune them. Oak wilt is caused by a fungus (Ceraticystis fagacearum) that is spread by Nitidulid (sap) beetles. These beetles are most active during the spring months, generally from February through May. By not pruning oak trees during this period, sap from the pruning will not attract the insects and provide an easy access for the fungus to get inside the tree. The best time to prune oaks is November through January when the beetles are least active. If making a pruning cut during sap flow, cover the wound with a sealant like a warm wax or pitch specially made for sealing tree grafts and wounds.
Maples (Acer)
Maples are pretty forgiving and do not necessarily have any special considerations for pruning and trimming. The only exceptions are to avoid pruning maples in the early spring or when they are not healthy. Maple trees move large amounts of sap in the spring and if a cut is made during this time, the tree will bleed heavily. Later in the spring as the tree is budding and growing new leaves, they will not put as much energy into healing the wound as they put into growing their leaves, which could result in disease problems. This also applies to when maples drop their leaves in autumn. Silver maples (Acer saccharinum) grow suckers often if the tree is over pruned and those suckers can be trimmed at any time of the year.
Willow (Salix)
Willow trees, in general, are one tree that can be pruned just about anytime and anywhere. But like most trees, it’s usually best to prune when the tree is dormant in winter.
Keep in mind when pruning a willow:
- that whatever branch is cut off of a willow, many more will take its place.
- to aim for very basic results such as balancing the weight of the tree, removing dead or diseased wood, and removing suckers.
- be ready to accept whatever shape the tree takes and give the tree lots of room to grow.
Elm (Ulmus)
Elm trees need a lot of special consideration when it comes to pruning them because of Dutch elm disease (DED). The only real good time to avoid the spore causing DED from entering vulnerable wounds is in the very early spring. In fact, lots of cities have laws regarding when elms can be pruned to help contain the disease. Elm trees are pruned very similar to how other trees are pruned. Remove old, dead wood, crossing and suckering branches, and other unsightly, unbalanced growth. Good pruning at the right time can help the elm fight off DED and recover from infections.
Poplar (Populus)
Poplar trees are best pruned when they are entering dormancy in the late summer and autumn. This time is also good because they will not put forth the energy to grow suckers. When pruning poplars, take great care to approach cuts with an “easy-does-it” attitude. Avoid tearing bark. To prune poplar correctly, cut the weight off of the branch gradually before making the final cut. Regular pruning of these fast-growing trees will extend their life and create a nice looking mature specimen.
Conifers
Conifers are generally trees that do not require a lot of pruning or trimming, and do not recover well after pruning. The two main reasons to prune a conifer are for health (removing of old, dead, diseased growth) and for size control (which is avoidable by planting a conifer at a place that is the right size for the mature tree).
When and how a conifer is pruned depends on the species.
- Arborvitaes (Thuja),Chamaecyparis, and junipers (Juniperus) should be pruned to keep their size only. Best done in late spring and early summer. The old wood underneath green growth will not grow back.
- Pines (Pinus) should be pruned by cutting off the candles in late spring to encourage bud formation for next year’s new growth.
- Hemlocks (Tsuga), yews (Taxus), firs (Abies), and spruces (Picea) should be pruned by trimming from late summer to late winter when the tree is dormant. Prune to control height by trimming the leader about a half inch above a bud on the leader. This will encourage branching while controlling height.
Hardwood Trees and Shrubs Without Showy Flowers
Prune these trees in the dormant season to:
- easily visualize the structure of the plant,
- maximize wound closure in the growing season after pruning,
- reduce the chance of transmitting disease,
- discourage excessive sap flow from the pruning wounds.
Flowering Trees and Shrubs
These can be pruned during the dormant season for the same reasons stated above. However, to preserve the current year's flower crop, prune according to the following schedule:
- Trees and shrubs that flower in spring, such as redbud (Cercis) and dogwood (Cornus), etc. should be pruned immediately after flowering.
- Trees and shrubs that flower in the summer or fall should be pruned during the dormant season. Flower buds will form on new twigs during the next growing season.
- Dead branches can be removed any time of the year.
- Many flowering trees are susceptible to fire blight, a bacterial disease that can be spread during pruning. These trees include many varieties of crabapple (Malus), hawthorn (Crataegus), pear (Pyrus), mountain ash (Sorbus), flowering quince (Cydonia) and Pyracantha. They should be pruned during the dormant season and the pruning tools should be cleaned with alcohol after every tree.
Source
"All Things Trees blog”, American Tree Service Supply, 2013.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Mulching Trees
Edited by Len Phillips
The use of organic mulches in the landscape is intended to duplicate the leaves in deciduous forests where they are annually deposited on the forest floor. Leaves act to insulate the soil in winter and are the mechanism by which carbon and mineral nutrients are recycled into the soil. The decaying leaves provide food for all the creatures that live in the forest soil.
Mulch Types
Mulch can be anything that will facilitate the survival of microorganisms in the soil, conserve soil moisture, and reduce weed growth in competition with the tree. Mulch can be any locally available product that will simulate the conditions of the forest floor. Though there is no single best mulch, except leaves from the forest trees, organic mulches are better for the tree and the ecology of the soil. Mulch from coniferous plants is best for placement over the roots of conifers, and hardwood mulch is considered the best for around hardwood trees.
There are two basic categories of mulch – organic and inorganic.
Organic Mulch
Organic mulches include whole leaves and shredded leaves, wood chips, shredded or chunk pine bark, pine needles, lumber yard wood waste, composted yard waste, buckwheat hulls, nut shells, ground corn cobs, cocoa shells, composted animal manure, and garden composts.
Benefits of Organic Mulch
Organic mulches provide many benefits to the soil as well as to tree growth. Organic mulch:
Green mulch, such as chopped weeds and grass clippings, will provide many of the benefits mentioned above. However, it will compete with the tree for water and nutrients until the mulch breaks down and returns the nutrients to the soil at a lower level where the plant roots need them and in a form the roots can absorb.
Inorganic Mulch
Inorganic mulch does not become part of the soil and breaks down over time. Inorganic mulches include volcanic or lava rock, crushed coral, pea gravel, crushed brick, and river rocks. They will not improve the microorganism activity in the soil.
Benefits of Inorganic Mulch
Since inorganic mulches, such as rubber crumbs, sands or rock, add nothing to the soil; they are less desirable than organic mulches. Inorganic mulches have applications in locations where organic mulches might blow away or the soil is not suitable for growing plants. The major benefit is that inorganic mulch has a much longer lifespan.
Mulch Color
Mulch color has become very popular in recent years. Colored mulch is made from processed wood chips. There are two types of coloring systems, one wet and the other dry. Both systems add color during the final grinding. The dry process adds less water to the wood chips than the wet process. The wet system is much easier to use and provides a higher quality product. The dry system allows the chips to dry faster so there is less chance of mold and there is less spillage of dye from the chipper.
No longer does red mulch indicate it is pine bark. It could be twice processed deciduous wood chips with iron dye added to give it the red color. Black mulch does not indicate the mulch is processed compost. It could be reground wood chips with carbon dye added to provide the black color. Brown mulch could be the natural color of freshly processed natural wood and bark or it could be the carbon and iron dyes mixed together to make brown. Color will greatly enhance the value of the mulch. Not only will the sale of the product be much greater than the natural wood chip, but lower quality mulch can also be colored to make it more saleable.
The content of mulch coloring is not always known and these chemicals can leach into the soil with unknown consequences for soil/plant health.
Mulch Depth
Coarse-textured mulches, such as wood chips, should be placed 2 – 3 inches (5 – 8 cm) deep annually to allow good oxygen diffusion into the soil. Finer-textured mulch such as shredded bark or buckwheat hulls, should only be a 1 – 2 inches (2½ – 5 cm) layer. On poorly drained or wet soils, mulch depths should not exceed 2 inches (5 cm), especially for shallow-rooted plants and trees.
Renewing mulch layers periodically should be done with as much care as the first layer. A light raking of existing mulch may be all that is needed to break through the layers. One to two inches (2½ – 5 cm) of new mulch is usually sufficient. The additional mulch will replace the mulch layer at the soil surface which decomposed during the previous growing season.
Newly planted trees should have mulch in the saucers 3 – 4 inches (8 – 10 cm) deep to form a 3 – 6 foot (1 – 2 m) diameter circle around the tree. As the tree becomes larger, expand the mulch to a 10 – 12 foot (3 – 4 m) diameter ring.
Mulch applied in the early winter, before the snow, but after the frost will provide maximum protection to the soil microorganisms and tender plants. An application of 1 – 2 inches of mulch in early winter will also suppress early emergence of perennial weeds in the spring.
Excessive Mulch
Excessive use of piled mulch, such as "volcanoes", which are cones of mulch creeping up the trunk of a tree, can induce fermentation, immobilize nutrients, increase the amount of moisture next to the trunk, cut off the oxygen supply, and kill the tree from stress. The application of excessive mulch is common where mulch is used decoratively around a tree. Tree roots, find more oxygen, will often grow above the soil surface and into the mulch. This makes those roots and the tree, more susceptible to drought, temperature extremes, frost heaving, and bark abrasion, especially if using inorganic mulches. Trees that have been wounded on the stem are predisposed to stem canker pathogens if the mulch is covering the wound. Trees are also prone to form adventitious roots in excess mulch that develop into stem girdling roots. These effects of over-mulching are not immediately observed, so it may take a few years for the effects to be noticed and by then, it may be too late.
Current guidelines suggest keeping mulch from touching all tree and plant trunks and stems. As a rule of thumb, keep mulch 3 to 5 inches (8 – 12 cm) away from young trees and 8 to 12 inches (20 – 30 cm) away from mature tree trunks. If mulch volcanoes are observed in the landscape, pull them down and away from the stems and spread them out over a larger area on the ground.
Problems with Mulch
Despite all the benefits that mulch supplies to trees, there are some major problems:
Acidic Mulch
"Sour" mulch can occur when mulch is piled very deep and this prevents an adequate air exchange. Without adequate oxygen, anaerobic microorganisms become active and cause the mulch to give off foul odors and produce extremely acidic pH levels. This mulch is highly toxic to plants. Avoid using it until it is properly composted and aerated.
Researchers have found that the continuous use of the same type of mulch does not change the soil's acidity level. So-called acidic mulches like pine bark may have a pH of 3.5 – 4.5 during the composting process, but when the composting is finished the pH is close to neutral.
Allelopathic Toxins
Allelopathic toxins are compounds produced by plants that inhibit the growth of other plants. The classic example of allelopathy is found in the black walnut (Juglans nigra). It produces juglone and juglonic acid, which inhibit the growth of many plants and trees that could become competition for the walnut. Fresh wood chips from black walnut trees should not be used as mulch unless well composted. Other allelopathic mulches include uncomposted sawdust of redwood (Sequoia) and cedar (Cedrus) and the bark of spruce (Picea), larch (Larix), and Douglas fir (Pseudotsuga). Once the wood chips have decomposed, the toxins have lost their potency.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Edited by Len Phillips
The use of organic mulches in the landscape is intended to duplicate the leaves in deciduous forests where they are annually deposited on the forest floor. Leaves act to insulate the soil in winter and are the mechanism by which carbon and mineral nutrients are recycled into the soil. The decaying leaves provide food for all the creatures that live in the forest soil.
Mulch Types
Mulch can be anything that will facilitate the survival of microorganisms in the soil, conserve soil moisture, and reduce weed growth in competition with the tree. Mulch can be any locally available product that will simulate the conditions of the forest floor. Though there is no single best mulch, except leaves from the forest trees, organic mulches are better for the tree and the ecology of the soil. Mulch from coniferous plants is best for placement over the roots of conifers, and hardwood mulch is considered the best for around hardwood trees.
There are two basic categories of mulch – organic and inorganic.
Organic Mulch
Organic mulches include whole leaves and shredded leaves, wood chips, shredded or chunk pine bark, pine needles, lumber yard wood waste, composted yard waste, buckwheat hulls, nut shells, ground corn cobs, cocoa shells, composted animal manure, and garden composts.
Benefits of Organic Mulch
Organic mulches provide many benefits to the soil as well as to tree growth. Organic mulch:
- improves soil aeration and soil structure as soil microorganisms break down,
- moderates extremes in surface soil temperatures,
- will degrade pesticides and other contaminants,
- minimizes weed competition with tree roots,
- effectively reduces soil erosion,
- conserves soil moisture,
- will increase soil fertility,
- can help detoxify soils,
- restricts soil cracking,
- can reduce salt buildup,
- can reduce soil crusting,
- reduces soil compaction,
- can reduce maintenance costs,
- allows rainwater penetration into the soil,
- will protect the trunk from mowers and weed whips,
- will provide a habitat for active and diverse microorganism populations,
- will encourage trees to grow significantly faster and healthier than non-mulched trees.
Green mulch, such as chopped weeds and grass clippings, will provide many of the benefits mentioned above. However, it will compete with the tree for water and nutrients until the mulch breaks down and returns the nutrients to the soil at a lower level where the plant roots need them and in a form the roots can absorb.
Inorganic Mulch
Inorganic mulch does not become part of the soil and breaks down over time. Inorganic mulches include volcanic or lava rock, crushed coral, pea gravel, crushed brick, and river rocks. They will not improve the microorganism activity in the soil.
Benefits of Inorganic Mulch
Since inorganic mulches, such as rubber crumbs, sands or rock, add nothing to the soil; they are less desirable than organic mulches. Inorganic mulches have applications in locations where organic mulches might blow away or the soil is not suitable for growing plants. The major benefit is that inorganic mulch has a much longer lifespan.
Mulch Color
Mulch color has become very popular in recent years. Colored mulch is made from processed wood chips. There are two types of coloring systems, one wet and the other dry. Both systems add color during the final grinding. The dry process adds less water to the wood chips than the wet process. The wet system is much easier to use and provides a higher quality product. The dry system allows the chips to dry faster so there is less chance of mold and there is less spillage of dye from the chipper.
No longer does red mulch indicate it is pine bark. It could be twice processed deciduous wood chips with iron dye added to give it the red color. Black mulch does not indicate the mulch is processed compost. It could be reground wood chips with carbon dye added to provide the black color. Brown mulch could be the natural color of freshly processed natural wood and bark or it could be the carbon and iron dyes mixed together to make brown. Color will greatly enhance the value of the mulch. Not only will the sale of the product be much greater than the natural wood chip, but lower quality mulch can also be colored to make it more saleable.
The content of mulch coloring is not always known and these chemicals can leach into the soil with unknown consequences for soil/plant health.
Mulch Depth
Coarse-textured mulches, such as wood chips, should be placed 2 – 3 inches (5 – 8 cm) deep annually to allow good oxygen diffusion into the soil. Finer-textured mulch such as shredded bark or buckwheat hulls, should only be a 1 – 2 inches (2½ – 5 cm) layer. On poorly drained or wet soils, mulch depths should not exceed 2 inches (5 cm), especially for shallow-rooted plants and trees.
Renewing mulch layers periodically should be done with as much care as the first layer. A light raking of existing mulch may be all that is needed to break through the layers. One to two inches (2½ – 5 cm) of new mulch is usually sufficient. The additional mulch will replace the mulch layer at the soil surface which decomposed during the previous growing season.
Newly planted trees should have mulch in the saucers 3 – 4 inches (8 – 10 cm) deep to form a 3 – 6 foot (1 – 2 m) diameter circle around the tree. As the tree becomes larger, expand the mulch to a 10 – 12 foot (3 – 4 m) diameter ring.
Mulch applied in the early winter, before the snow, but after the frost will provide maximum protection to the soil microorganisms and tender plants. An application of 1 – 2 inches of mulch in early winter will also suppress early emergence of perennial weeds in the spring.
Excessive Mulch
Excessive use of piled mulch, such as "volcanoes", which are cones of mulch creeping up the trunk of a tree, can induce fermentation, immobilize nutrients, increase the amount of moisture next to the trunk, cut off the oxygen supply, and kill the tree from stress. The application of excessive mulch is common where mulch is used decoratively around a tree. Tree roots, find more oxygen, will often grow above the soil surface and into the mulch. This makes those roots and the tree, more susceptible to drought, temperature extremes, frost heaving, and bark abrasion, especially if using inorganic mulches. Trees that have been wounded on the stem are predisposed to stem canker pathogens if the mulch is covering the wound. Trees are also prone to form adventitious roots in excess mulch that develop into stem girdling roots. These effects of over-mulching are not immediately observed, so it may take a few years for the effects to be noticed and by then, it may be too late.
Current guidelines suggest keeping mulch from touching all tree and plant trunks and stems. As a rule of thumb, keep mulch 3 to 5 inches (8 – 12 cm) away from young trees and 8 to 12 inches (20 – 30 cm) away from mature tree trunks. If mulch volcanoes are observed in the landscape, pull them down and away from the stems and spread them out over a larger area on the ground.
Problems with Mulch
Despite all the benefits that mulch supplies to trees, there are some major problems:
- Freshly applied organic mulches and green mulch will tend to deplete soil nitrogen slightly and temporarily until the compost action is completed. At that point, the nitrogen becomes available for the trees. Adding supplemental nitrogen fertilizer to speed up the decomposition process, if desired, does not work and should be avoided.
- Mulch can provide a habitat in which rodents can live and be protected from predators. The rodents will use the mulch for cover while feeding on the tree bark, thus being another reason to keep the mulch away from the tree trunk.
- Certain fungi grow in dry compacted mulches and prevent water from penetrating the soil.
- Geotextile fabrics used as mulch or used to prevent weed growth and covered with mulch can lead to higher soil temperatures and shedding of rain and irrigation water and are no longer recommended. In addition, the fabric threads become covered with microbes that prevent moisture from passing through the fabric, thereby making the fabric impervious.
- Black plastic and peat moss can cause the same problems as geotextile fabric in addition to creating a moisture and soil oxygen barrier that causes root surfacing. They are also no longer recommended.
Acidic Mulch
"Sour" mulch can occur when mulch is piled very deep and this prevents an adequate air exchange. Without adequate oxygen, anaerobic microorganisms become active and cause the mulch to give off foul odors and produce extremely acidic pH levels. This mulch is highly toxic to plants. Avoid using it until it is properly composted and aerated.
Researchers have found that the continuous use of the same type of mulch does not change the soil's acidity level. So-called acidic mulches like pine bark may have a pH of 3.5 – 4.5 during the composting process, but when the composting is finished the pH is close to neutral.
Allelopathic Toxins
Allelopathic toxins are compounds produced by plants that inhibit the growth of other plants. The classic example of allelopathy is found in the black walnut (Juglans nigra). It produces juglone and juglonic acid, which inhibit the growth of many plants and trees that could become competition for the walnut. Fresh wood chips from black walnut trees should not be used as mulch unless well composted. Other allelopathic mulches include uncomposted sawdust of redwood (Sequoia) and cedar (Cedrus) and the bark of spruce (Picea), larch (Larix), and Douglas fir (Pseudotsuga). Once the wood chips have decomposed, the toxins have lost their potency.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
Living Mulch
By Len Phillips
In the practice of general plant care, a living mulch is a ground cover plant growing at the base of a tree. Living mulches are sometimes used at locations where the tree is growing in a sidewalk cut-out and the living mulch (plants) are growing around the tree. The living mulch is intended to beautify and replace the need for a tree grate or conventional mulch by using plants to provide weed suppression, control of the soil temperature, and a visual means to discourage people from walking close to the tree and causing soil compaction. Living mulches can reduce water runoff and erosion, and filter surface water runoff for use by the tree. Living mulches have also been shown to increase the population of organisms which enhances the quality of the soil. Living mulches are intended to grow for many years in harmony with the tree. Opponents of this concept believe the living mulch robs the tree of soil moisture, nutrients, and microorganisms. But the fact is that these plants help the tree by preventing soil compaction from foot traffic and evaporation of soil moisture by converting nutrients into forms that are useful for the tree.
Plant selection for creating a living mulch is not an easy task. While just about any plant might grow in harmony with a tree in a conventional landscape, very few will thrive living in the sidewalk cutout surrounded by concrete. The planting of the ground covers may occur anytime including right after the tree has been planted. The plants should be planted on a grade of no more than 1 inch (2.5 cm) below the sidewalk elevation to hold runoff water for the plants and the tree. The living mulch plants should be carefully placed around the outside edge of the sidewalk cutout to avoid any conflict with the newly developing tree roots and the underground root stabilizing system.
Never plant anything within 12" (30 cm) of the flare. No part of the tree's trunk and bark should ever be covered with anything that retains moisture. Doing so encourages rot. In addition, any planting of small ground covers needs to be done carefully so as not to damage the existing tree's roots. Open areas should still be mulched with composted wood chips so the soil is never left bare.
Most Desirable Living Mulches
The following, in this author's opinion, are the best living mulches because they are vigorous ground covers and will tolerate pedestrian traffic, winter snowplow damage, and erratic weather conditions.
White clover Trifolium repens - Clovers with their deep roots, provide resistance to soil compaction. Legume living mulches also have some important positive effects on the nutrient cycling that benefit the tree. For example, clover fixes the atmospheric nitrogen that is important for tree growth, and it is effective for enhancing and recycling the soil's nutrients. Clover can grow in sun or shade, maintain a low profile, thrive if repeatedly mowed and it will withstand foot traffic. It is considered by many as the best choice for a living mulch. In established stands, it also may provide some nitrogen suitable for use by the tree.
Vinca Vinca minor - Vinca does well in all light conditions and, once established, is fairly tolerant of a less than desirable site and soil conditions. Vinca is a shallow rooted creeper that tolerates soil compaction and pedestrian foot traffic, once it is established. It should be planted with quart size plants that have large root systems to reduce the time for the plant to become established. These larger plants are quite developed and fewer plants are needed so there's a lot less disturbance in the sidewalk cutout area. Impact on the tree is minimal.
Creepers
Creepers are plants that can grow to cover the soil from the outside edge of the sidewalk cutout where there is more light, and they may grow toward the trunk of the tree with time. These are all shallow-rooted perennials with roots in the top 6 inches (15 cm) of soil, and therefore, above the tree's main roots. They are all tolerant of varying sun exposures. Creepers do require weeding and extra water for the first few years but once established, the plants look outstanding all year. All the plants cool the roots and discourage any compacting foot traffic. Reports indicate that there has to be some assumed nutrient competition between tree and the groundcover, but these reports also indicate that both the tree and the creepers appear to be living in harmony. Some of the best creepers for this function include:
Ajuga Ajuga reptans
Peanut Arachis repens
Epimedium Epimedium spp.
Wild Woodland Strawberry Fragaria vesca
Coral Bells Heuchera spp.
Mini and dwarf Hosta varieties
Yellowroot (Golden Seal) Hydrastis canadensis
Liriope Liriope musca
Cupflower Mazus reptans
Pachysandra Pachysandra
Ginseng Panax quinquefolius
Woodland Phlox Phlox divaricate
Stonecrop Sedum spp.
Comfrey Symphytum officinalis
Creeping Thyme Thymus serpyllum
Turkish Speedwell Veronica liwanensis
Barren Strawberry Waldsteinia ternate
Hardy Fern Several species are suitable for living mulch, especially in somewhat shady areas.
Undesirable Living Mulches
Not only are the plants listed below considered invasive in many locations, they can also cause moisture retention, root rot, and other problems for the tree. Many of these plants can also climb over the entire tree. NOT recommended are:
Porcelain Berry Ampelopsis brevipedunculata
Climbing Euonymus Euonymus fortunei
English Ivy Hedera helix
Kudzu Pueraria lobata
Bittersweet Solanum dulcamara
Poison Ivy Toxicodendron radicans
Grape Vitis spp.
Wisteria Wisteria spp.
Annuals – Growing annuals under young trees is the exception to being good for trees. Annuals are
aggressive growers and they can cause growth reduction to the tree because of the competition for soil nutrients. Annuals also need lots of water and weekly maintenance.
Shrubs – Often young trees have been planted and combined with nice flowering shrubs. Over time, the trees will win the competition and the shrubs look terrible and need to be removed, so they are not a good choice in the sidewalk cut out areas.
Creeping Juniper Juniperus horizontalis - a very popular group of junipers that require a lot of maintenance to keep them from growing over the flare and sidewalk, while also encouraging pest and disease problems causing harm to the tree. These problems are in addition to the problems mentioned above with annuals and shrubs.
Caution
Not all trees are created equal. Each requires specific light, soil, and moisture conditions to survive and remain healthy. Some tree species are extremely sensitive to major soil disturbance. Planting beneath trees that are sensitive to having their roots disturbed may need to have the proposed plantings scaled back or carried out over a few years.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.
By Len Phillips
In the practice of general plant care, a living mulch is a ground cover plant growing at the base of a tree. Living mulches are sometimes used at locations where the tree is growing in a sidewalk cut-out and the living mulch (plants) are growing around the tree. The living mulch is intended to beautify and replace the need for a tree grate or conventional mulch by using plants to provide weed suppression, control of the soil temperature, and a visual means to discourage people from walking close to the tree and causing soil compaction. Living mulches can reduce water runoff and erosion, and filter surface water runoff for use by the tree. Living mulches have also been shown to increase the population of organisms which enhances the quality of the soil. Living mulches are intended to grow for many years in harmony with the tree. Opponents of this concept believe the living mulch robs the tree of soil moisture, nutrients, and microorganisms. But the fact is that these plants help the tree by preventing soil compaction from foot traffic and evaporation of soil moisture by converting nutrients into forms that are useful for the tree.
Plant selection for creating a living mulch is not an easy task. While just about any plant might grow in harmony with a tree in a conventional landscape, very few will thrive living in the sidewalk cutout surrounded by concrete. The planting of the ground covers may occur anytime including right after the tree has been planted. The plants should be planted on a grade of no more than 1 inch (2.5 cm) below the sidewalk elevation to hold runoff water for the plants and the tree. The living mulch plants should be carefully placed around the outside edge of the sidewalk cutout to avoid any conflict with the newly developing tree roots and the underground root stabilizing system.
Never plant anything within 12" (30 cm) of the flare. No part of the tree's trunk and bark should ever be covered with anything that retains moisture. Doing so encourages rot. In addition, any planting of small ground covers needs to be done carefully so as not to damage the existing tree's roots. Open areas should still be mulched with composted wood chips so the soil is never left bare.
Most Desirable Living Mulches
The following, in this author's opinion, are the best living mulches because they are vigorous ground covers and will tolerate pedestrian traffic, winter snowplow damage, and erratic weather conditions.
White clover Trifolium repens - Clovers with their deep roots, provide resistance to soil compaction. Legume living mulches also have some important positive effects on the nutrient cycling that benefit the tree. For example, clover fixes the atmospheric nitrogen that is important for tree growth, and it is effective for enhancing and recycling the soil's nutrients. Clover can grow in sun or shade, maintain a low profile, thrive if repeatedly mowed and it will withstand foot traffic. It is considered by many as the best choice for a living mulch. In established stands, it also may provide some nitrogen suitable for use by the tree.
Vinca Vinca minor - Vinca does well in all light conditions and, once established, is fairly tolerant of a less than desirable site and soil conditions. Vinca is a shallow rooted creeper that tolerates soil compaction and pedestrian foot traffic, once it is established. It should be planted with quart size plants that have large root systems to reduce the time for the plant to become established. These larger plants are quite developed and fewer plants are needed so there's a lot less disturbance in the sidewalk cutout area. Impact on the tree is minimal.
Creepers
Creepers are plants that can grow to cover the soil from the outside edge of the sidewalk cutout where there is more light, and they may grow toward the trunk of the tree with time. These are all shallow-rooted perennials with roots in the top 6 inches (15 cm) of soil, and therefore, above the tree's main roots. They are all tolerant of varying sun exposures. Creepers do require weeding and extra water for the first few years but once established, the plants look outstanding all year. All the plants cool the roots and discourage any compacting foot traffic. Reports indicate that there has to be some assumed nutrient competition between tree and the groundcover, but these reports also indicate that both the tree and the creepers appear to be living in harmony. Some of the best creepers for this function include:
Ajuga Ajuga reptans
Peanut Arachis repens
Epimedium Epimedium spp.
Wild Woodland Strawberry Fragaria vesca
Coral Bells Heuchera spp.
Mini and dwarf Hosta varieties
Yellowroot (Golden Seal) Hydrastis canadensis
Liriope Liriope musca
Cupflower Mazus reptans
Pachysandra Pachysandra
Ginseng Panax quinquefolius
Woodland Phlox Phlox divaricate
Stonecrop Sedum spp.
Comfrey Symphytum officinalis
Creeping Thyme Thymus serpyllum
Turkish Speedwell Veronica liwanensis
Barren Strawberry Waldsteinia ternate
Hardy Fern Several species are suitable for living mulch, especially in somewhat shady areas.
Undesirable Living Mulches
Not only are the plants listed below considered invasive in many locations, they can also cause moisture retention, root rot, and other problems for the tree. Many of these plants can also climb over the entire tree. NOT recommended are:
Porcelain Berry Ampelopsis brevipedunculata
Climbing Euonymus Euonymus fortunei
English Ivy Hedera helix
Kudzu Pueraria lobata
Bittersweet Solanum dulcamara
Poison Ivy Toxicodendron radicans
Grape Vitis spp.
Wisteria Wisteria spp.
Annuals – Growing annuals under young trees is the exception to being good for trees. Annuals are
aggressive growers and they can cause growth reduction to the tree because of the competition for soil nutrients. Annuals also need lots of water and weekly maintenance.
Shrubs – Often young trees have been planted and combined with nice flowering shrubs. Over time, the trees will win the competition and the shrubs look terrible and need to be removed, so they are not a good choice in the sidewalk cut out areas.
Creeping Juniper Juniperus horizontalis - a very popular group of junipers that require a lot of maintenance to keep them from growing over the flare and sidewalk, while also encouraging pest and disease problems causing harm to the tree. These problems are in addition to the problems mentioned above with annuals and shrubs.
Caution
Not all trees are created equal. Each requires specific light, soil, and moisture conditions to survive and remain healthy. Some tree species are extremely sensitive to major soil disturbance. Planting beneath trees that are sensitive to having their roots disturbed may need to have the proposed plantings scaled back or carried out over a few years.
The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.
*Members of ISA may apply the 0.5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 0.5 BCMA Practice credits.
California UFC members will receive credit for passing the test. Please add your CaUFC number after your ISA and/or SAF certification number.
ASCA members may submit your ISA certification record to the ASCA and receive credits one for one.
MTOA members must follow the ISA instructions indicated above.
To take the test by the pay per test option, click on the 'Pay Now' button below where you can send payment online securely with your credit card or Pay Pal account. After your payment is submitted, click on ‘Return to Merchant' / gibneyCE.com. That will take you to the test sign in page followed by the test. Members with certifications from both ISA and SAF, please be sure to add both of your certification numbers. These numbers are important for reporting purposes.
To take the test as an annual subscriber with reduced rates, click on Password and enter your test password which will take you to the test sign in page. If you would like to become a subscriber see our Annual Subscription page for details.
When you have finished answering all questions you will be prompted to click ‘next’ to send your answers to gibneyCE.com. You can then click ‘next’ to view your test summary. A test review of your answers is available upon request.
All passing test scores are sent from gibneyCE.com to your organization(s) at the end of every month and they will appear on your certification record 4 to 6 weeks* after that. ISA maintains a record of CEU credits on their website.
*SAF requires 5 passing test scores before reporting.
Test re-takes are allowed, however you will have to pay for the retake if you are using the pay per test option. You can spend as much time as you would like to take the test but it is important not to leave the test site until you have answered all the questions and see the 'sending your answers' response.