Seminar #97 from Online Seminars for Municipal Arborists
January - March 2023
Sections Go directly to the section by clicking on the title below
January - March 2023
Sections Go directly to the section by clicking on the title below
Note: Click on green text in each section for more information and photos.
RECOMMENDED TREE PLANTING SUGGESTIONS AND GUIDELINES
Compiled by Len Phillips
This list was prepared during some discussions among tree planting experts on LinkedIn's Urban Forestry Discussion Group as the best way to successfully install a tree.
1. Before a tree is purchased, be sure there is a defined maintenance program to ensure survival and longevity
for the new tree. Be sure the soil is tested to ensure there are no deficiencies, the soil is suitable for the tree,
and there is sufficient soil volume available. Some locations may require a water quality test as well. If the soil
and species selection do not match, then even a properly planted will not thrive.
2. Have a plan to install and grow trees properly using the A300 standard so everyone involved with the care of
the tree is held to that standard. Consider using organics, biochar and mycorrhizae to make a good relationship
with the soil even better.
3. Local laws require contacting the local utility location marking services for all utilities above and below ground.
Be sure the utility locations are safe, a suitable distance from the utilities, and clearly marked before tree
planting.
4. Select the right tree, for the right spot and the right soil considering land use and the amount of sunlight for the
tree. Choose a cultivar of the native tree that has been selected for the site because cultivars are usually
better than the native tree. "Better" means a better form or a better color, or better pest and disease
resistance, or better tolerance to global warming, etc.
5. Dig the hole as deep as necessary to be sure the bottom of the flare will be at the finished grade. Remove all
wire and burlap entirely from the root ball when it is in the hole.
6. The tree should be inspected to be sure it has almost all of its fibrous roots and no girdling roots. The tree roots
should be the highest quality possible. If the tree is growing in a fabric grow bag it should have many, good
quality roots visible when the bag is removed. If the tree is growing in a container, all the soil should be
washed off the roots and the tree planted as a bare root tree, using the local soil.
7. When installing trees bare root, being sure ALL the tiny root hairs are kept wet at ALL times.
8. Once the tree is installed, check that the flare is at finished grade and the tree has been watered thoroughly.
9. Use root stabilizers instead of guying unless above ground posts are necessary to provide other protective
functions. Root stabilizers hold the tree in place and promote rapid root growth. Wooden stabilizer removal is
optional. The same for the metal “Tree Staple”.
10. Keep the soil moist with water bags filled every other day, until new leaves have sprouted or have a person
water the tree by rain or manually every other day if there is insufficient rainfall.
11. Inspect the tree's health and growth rate weekly for the first year after the installation.
12. Structural pruning of the branches between the installation date and the first year after planting by a person
trained in pruning for proper long-term tree structure.
13. Long-term maintenance is essential in an urban environment including a yearly check on the health of the
tree.
14. If the anticipated tree care cannot follow this plan, encourage the planting of native perennials, shrubs and
groundcovers instead.
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, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 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.
Compiled by Len Phillips
This list was prepared during some discussions among tree planting experts on LinkedIn's Urban Forestry Discussion Group as the best way to successfully install a tree.
1. Before a tree is purchased, be sure there is a defined maintenance program to ensure survival and longevity
for the new tree. Be sure the soil is tested to ensure there are no deficiencies, the soil is suitable for the tree,
and there is sufficient soil volume available. Some locations may require a water quality test as well. If the soil
and species selection do not match, then even a properly planted will not thrive.
2. Have a plan to install and grow trees properly using the A300 standard so everyone involved with the care of
the tree is held to that standard. Consider using organics, biochar and mycorrhizae to make a good relationship
with the soil even better.
3. Local laws require contacting the local utility location marking services for all utilities above and below ground.
Be sure the utility locations are safe, a suitable distance from the utilities, and clearly marked before tree
planting.
4. Select the right tree, for the right spot and the right soil considering land use and the amount of sunlight for the
tree. Choose a cultivar of the native tree that has been selected for the site because cultivars are usually
better than the native tree. "Better" means a better form or a better color, or better pest and disease
resistance, or better tolerance to global warming, etc.
5. Dig the hole as deep as necessary to be sure the bottom of the flare will be at the finished grade. Remove all
wire and burlap entirely from the root ball when it is in the hole.
6. The tree should be inspected to be sure it has almost all of its fibrous roots and no girdling roots. The tree roots
should be the highest quality possible. If the tree is growing in a fabric grow bag it should have many, good
quality roots visible when the bag is removed. If the tree is growing in a container, all the soil should be
washed off the roots and the tree planted as a bare root tree, using the local soil.
7. When installing trees bare root, being sure ALL the tiny root hairs are kept wet at ALL times.
8. Once the tree is installed, check that the flare is at finished grade and the tree has been watered thoroughly.
9. Use root stabilizers instead of guying unless above ground posts are necessary to provide other protective
functions. Root stabilizers hold the tree in place and promote rapid root growth. Wooden stabilizer removal is
optional. The same for the metal “Tree Staple”.
10. Keep the soil moist with water bags filled every other day, until new leaves have sprouted or have a person
water the tree by rain or manually every other day if there is insufficient rainfall.
11. Inspect the tree's health and growth rate weekly for the first year after the installation.
12. Structural pruning of the branches between the installation date and the first year after planting by a person
trained in pruning for proper long-term tree structure.
13. Long-term maintenance is essential in an urban environment including a yearly check on the health of the
tree.
14. If the anticipated tree care cannot follow this plan, encourage the planting of native perennials, shrubs and
groundcovers instead.
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, Municipal Specialist, Tree Worker/Climber, Tree Worker/Aerial Lift, or 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 More Trees is Not the Answer
Edited by Len Phillips
Carbon dioxide (CO2) is being released into the atmosphere, which is causing our planet to continue getting warmer. While trees do absorb CO2, they are not the total solution to the problem of an excess amount of CO2 in the atmosphere. Scientific calculations indicate that we cannot plant enough trees to take back all the CO2 that mankind has already produced and released into the atmosphere. Unfortunately, while the idea sounds reasonable and definitely helps to some extent, it will not be enough to counter-balance the amount of fossil fuels being burned and the amount of CO2 still being produced by our vehicles every day. Several scientific papers have supported mass tree-planting to store more carbon in the soil, in a process known as carbon sequestration. Using trees to sequester carbon in the soil is a good idea, but it is not enough to offset the carbon added to the atmosphere by human activities.
As arborists, foresters, and landscape architects all know, trees grow and absorb CO2 from the air and soil. They use that carbon to grow their leaves, wood, and roots. So, it makes sense to plant trees to reduce the CO2 in the atmosphere, but it is just not enough. The soil carbon remains even after the trees die.
In mature forests, the uptake of CO2 is by photosynthesis. It is balanced by the release of CO2 back to the atmosphere through the decay of wood and leaves, plus the consumption by insects and animals, and respiration within the trees themselves. Furthermore, forests have metabolisms just like people. As they approach maturity, forests reach an equilibrium where they are carbon neutral. If the tree is allowed to die and rot away on the forest floor or burn in a wildfire, the carbon is released back into the atmosphere.
Recently, people have taken this logic to an extreme. For example, a bill titled the “Trillion Trees Act” introduced in the U.S. Congress aims to plant one trillion trees by 2050. But there are several issues with this bill, and nearly every single environmental organization in the U.S. co-signed a letter of opposition. The primary issue is that this bill detracts from needed total reductions in all fossil fuel emissions.
The benefits of planting trees also depends on what we do with them. The Trillion Trees Act, for example, would open up all sorts of forests to logging, or to turn the new trees into paper or wood, but it would not consider changes to soil carbon. While some carbon can be stored long-term in wood products, harvesting trees from a forest without thoughtful management can actually decrease the carbon stored in the forest. Thus, making no improvement in global warming.
Instead of planting more trees, tree care professionals should focus their efforts on stopping the many ways that existing forests are destroyed. Mature forests with many species of trees do the best job of storing carbon. Peat soils in forests build up pure organic carbon, which keeps a lot of CO2 out of the atmosphere. However, these forests have been destroyed in many locations and this results in the release of all of their stored carbon.
Individuals can help prevent the release of carbon stored in forests by discouraging the decision makers at the federal and state levels from supporting policies that encourage deforestation. People can also help prevent the destruction of forest and the release of its stored carbon by not purchasing unnecessary wood and paper products.
Studies have estimated an average American’s carbon footprint is at around 16 tons of CO2 annually. This is one of the highest figures for a person in any country on Earth because of the energy-intensive American lifestyle. A single mature tree, meanwhile, may absorb about 50 pounds of carbon dioxide per year. At this rate, it would take 640 trees per person to account for all the American emissions of carbon, which adds up to more than 200 billion trees. A recent study estimated there are about 3 trillion trees on Earth right now.
As part of the planet’s natural carbon cycle, carbon sinks such as the growing forests and oceans absorb an enormous amount of naturally emitted CO2 as well as much of what humans create. Humanity’s emissions however have tipped that natural cycle out of balance. And the enormous complexity of this system makes it almost impossible to say for sure how many new trees would be required to bring it back into balance.
An MIT professor of civil and environmental engineering explains that although it is a good idea for the world to plant many more trees, the truth is much more complicated than assuming more trees can cancel out our emissions. One key question is: “How much treeless land is available for planting?” Dense forests once covered the American Midwest, for example. They could grow there again, but much of that treeless land is now used for cities, agriculture, and industry.
Even if the United States could find the space to plant about 200 billion new trees, it would not reap the climate benefits immediately. The faster trees are growing, the more carbon they can suck up, which means new growth is not as valuable a carbon sink as are longstanding forests. Also, trees do not last forever. When they die and decay, burn in a wildfire, or are chopped down and burned for fuel, these trees release all the CO2 they’ve been hiding away. There are exceptions to this rule because there are some studies of peat forests in places like the peat swamp forests of Borneo, where biomass accumulates on the forest floor rather than fully decaying and releasing its CO2.into the air. But most forests cannot theoretically sequester carbon forever.
It is also not clear that trees could continue to soak up CO2 indefinitely if we humans continue our emissions unabated. Trees in healthy forests need not only carbon dioxide but also nutrients from the soil like nitrogen and phosphorus to grow. Researchers have shown that trees will need much more of both nutrients to balance their diets as the CO2 concentration in the atmosphere increases. If the soil does not have enough, that could curtail as much CO2 as a tree is able to soak up.
For all these reasons, a society would do better by focusing on preserving existing forests rather than prioritizing new growth to offset emissions. Planting trees where there are none is a good idea and that will take up CO2. However, a similar if not greater amount of carbon dioxide can be kept out of the atmosphere by preserving the existing forests and reducing the number of trees cut down. It's almost silly to think about planting a huge number of new trees while we're just burning and destroying them elsewhere. The burning is releasing carbon at rates that are much higher than what new growth would take up.
Source
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
Edited by Len Phillips
Carbon dioxide (CO2) is being released into the atmosphere, which is causing our planet to continue getting warmer. While trees do absorb CO2, they are not the total solution to the problem of an excess amount of CO2 in the atmosphere. Scientific calculations indicate that we cannot plant enough trees to take back all the CO2 that mankind has already produced and released into the atmosphere. Unfortunately, while the idea sounds reasonable and definitely helps to some extent, it will not be enough to counter-balance the amount of fossil fuels being burned and the amount of CO2 still being produced by our vehicles every day. Several scientific papers have supported mass tree-planting to store more carbon in the soil, in a process known as carbon sequestration. Using trees to sequester carbon in the soil is a good idea, but it is not enough to offset the carbon added to the atmosphere by human activities.
As arborists, foresters, and landscape architects all know, trees grow and absorb CO2 from the air and soil. They use that carbon to grow their leaves, wood, and roots. So, it makes sense to plant trees to reduce the CO2 in the atmosphere, but it is just not enough. The soil carbon remains even after the trees die.
In mature forests, the uptake of CO2 is by photosynthesis. It is balanced by the release of CO2 back to the atmosphere through the decay of wood and leaves, plus the consumption by insects and animals, and respiration within the trees themselves. Furthermore, forests have metabolisms just like people. As they approach maturity, forests reach an equilibrium where they are carbon neutral. If the tree is allowed to die and rot away on the forest floor or burn in a wildfire, the carbon is released back into the atmosphere.
Recently, people have taken this logic to an extreme. For example, a bill titled the “Trillion Trees Act” introduced in the U.S. Congress aims to plant one trillion trees by 2050. But there are several issues with this bill, and nearly every single environmental organization in the U.S. co-signed a letter of opposition. The primary issue is that this bill detracts from needed total reductions in all fossil fuel emissions.
The benefits of planting trees also depends on what we do with them. The Trillion Trees Act, for example, would open up all sorts of forests to logging, or to turn the new trees into paper or wood, but it would not consider changes to soil carbon. While some carbon can be stored long-term in wood products, harvesting trees from a forest without thoughtful management can actually decrease the carbon stored in the forest. Thus, making no improvement in global warming.
Instead of planting more trees, tree care professionals should focus their efforts on stopping the many ways that existing forests are destroyed. Mature forests with many species of trees do the best job of storing carbon. Peat soils in forests build up pure organic carbon, which keeps a lot of CO2 out of the atmosphere. However, these forests have been destroyed in many locations and this results in the release of all of their stored carbon.
Individuals can help prevent the release of carbon stored in forests by discouraging the decision makers at the federal and state levels from supporting policies that encourage deforestation. People can also help prevent the destruction of forest and the release of its stored carbon by not purchasing unnecessary wood and paper products.
Studies have estimated an average American’s carbon footprint is at around 16 tons of CO2 annually. This is one of the highest figures for a person in any country on Earth because of the energy-intensive American lifestyle. A single mature tree, meanwhile, may absorb about 50 pounds of carbon dioxide per year. At this rate, it would take 640 trees per person to account for all the American emissions of carbon, which adds up to more than 200 billion trees. A recent study estimated there are about 3 trillion trees on Earth right now.
As part of the planet’s natural carbon cycle, carbon sinks such as the growing forests and oceans absorb an enormous amount of naturally emitted CO2 as well as much of what humans create. Humanity’s emissions however have tipped that natural cycle out of balance. And the enormous complexity of this system makes it almost impossible to say for sure how many new trees would be required to bring it back into balance.
An MIT professor of civil and environmental engineering explains that although it is a good idea for the world to plant many more trees, the truth is much more complicated than assuming more trees can cancel out our emissions. One key question is: “How much treeless land is available for planting?” Dense forests once covered the American Midwest, for example. They could grow there again, but much of that treeless land is now used for cities, agriculture, and industry.
Even if the United States could find the space to plant about 200 billion new trees, it would not reap the climate benefits immediately. The faster trees are growing, the more carbon they can suck up, which means new growth is not as valuable a carbon sink as are longstanding forests. Also, trees do not last forever. When they die and decay, burn in a wildfire, or are chopped down and burned for fuel, these trees release all the CO2 they’ve been hiding away. There are exceptions to this rule because there are some studies of peat forests in places like the peat swamp forests of Borneo, where biomass accumulates on the forest floor rather than fully decaying and releasing its CO2.into the air. But most forests cannot theoretically sequester carbon forever.
It is also not clear that trees could continue to soak up CO2 indefinitely if we humans continue our emissions unabated. Trees in healthy forests need not only carbon dioxide but also nutrients from the soil like nitrogen and phosphorus to grow. Researchers have shown that trees will need much more of both nutrients to balance their diets as the CO2 concentration in the atmosphere increases. If the soil does not have enough, that could curtail as much CO2 as a tree is able to soak up.
For all these reasons, a society would do better by focusing on preserving existing forests rather than prioritizing new growth to offset emissions. Planting trees where there are none is a good idea and that will take up CO2. However, a similar if not greater amount of carbon dioxide can be kept out of the atmosphere by preserving the existing forests and reducing the number of trees cut down. It's almost silly to think about planting a huge number of new trees while we're just burning and destroying them elsewhere. The burning is releasing carbon at rates that are much higher than what new growth would take up.
Source
- Stein, Paige, “Protecting Urban Parks from the Impacts of Climate Change”, Yale School of the Environment.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
Regeneration of Trees
Ethan Tapper
Whether by natural or human activity, when a disturbance causes harm to trees, the tree becomes very stressed. Forest stewards realize that the tree may seem to be ugly, empty, and hopeless. However, if we allow ourselves to look beyond the mess and consider an understanding of what the trees are and how they work, we can see that these moments are opportunities for the forest to showcase the miracle of regeneration, and the many benefits that come with it.
When light and space is made available in the city as well as the forest canopy, it is inevitable that regeneration and the growth of new trees and plants will occur. Disturbances are more than something that forests endure. Ever since there have been forests, there have been fires, windstorms, ice storms, and insect and disease outbreaks. As jarring as they may be to us, forests need disturbances. Forests and the thousands of species that comprise them, have adapted to these disturbances and they are a critical part of how forests change over time, how they become diverse and complex, and how they provide habitat for wildlife.
The miracle of regeneration is the evolutionary response of the forest community to a dynamic world. Light, the currency of the forest, is usually controlled by trees, their broad canopies casting the understory in shade. The death of trees, is a disturbance that creates openings in the forest canopy allowing some of this precious light to reach the forest floor, creating an opportunity for new trees to establish and to grow towards the riches of the canopy and sunlight.
Each tree and plant species in a forest occupies a complex ecological niche. One of the ways that trees’ niches are defined is by the light levels under which they are most competitive. Shade-intolerant species like white birch (Betula papyrifera) and aspen or poplar (Populus nigra) require very large openings, such as those caused by a large-scale or catastrophic disturbances, whereas shade-tolerant species like beech (Fagus), sugar maple (Acer saccharum) and hemlock (Tsuga canadensis) can grow in near or complete shade. Mid-tolerant species like white ash (Fraxinus americana), red oak (Quercus rubra) and yellow birch (Betula alleghaniensis) compete best in mid-sized openings, too small for shade-intolerant trees and too big for slow-growing shade-tolerant trees to be competitive.
Trees are also adapted to occupy a variety of other nitches such as different soil types and depths, on different slopes and aspects. Yellow birch and hemlock seedlings often grow on rotting “nurse logs,” or on the upturned roots of fallen trees. White pine (Pinus strobus) seedlings colonize scarified or disturbed soils, whereas the sugar maple does best with a deep layer of decomposing leaves. Red oak and white ash establish advance regeneration seedlings which may wait in the understory for a decade or more, ready to shoot upwards in the event of a disturbance. Cherries (Prunus), raspberries (Rubus) and blackberries (Rubus) produce seeds that can remain viable but not germinated in forest soils for decades, only sprouting following a wildfire or other disturbance, that leaves a burst of sunlight on the forest floor.
While it is intuitive to think of regeneration as a means to an end. The process by which dead trees are replaced by living trees has tremendous value to the forest community. As a forest regenerates, it passes through many different stages, each of which provides unique habitat; used by wildlife from the insectivorous birds that hunt in canopy gaps, to the pollinators that visit the diversity of herbaceous plants in flower. Each step in this continuum of change is normal, natural and important to a wide range of living things.
Understanding the miracle of regeneration, and the benefits it brings, can change the way that we think about disturbances in the forest. Whether it’s a windstorm or a forest management project. Forests are built on change: every old growth forest was once a young forest and will be once again, and every tree in the woods is the legacy of the death of a tree and the memory of a disturbance.
While it is incredible to witness the resiliency of a forest, how it responds to adversity with regeneration and renewal, this resilience is not limitless. The miracle of regeneration is threatened by invasive plants, pests and pathogens, by over populations of deer, by climate change, by forest fragmentation and by deforestation. In this moment it is critical that we act not just to protect forests but also to protect their ability to regenerate, to adapt, to change, and to remake themselves for the world of the future.
Source
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
Ethan Tapper
Whether by natural or human activity, when a disturbance causes harm to trees, the tree becomes very stressed. Forest stewards realize that the tree may seem to be ugly, empty, and hopeless. However, if we allow ourselves to look beyond the mess and consider an understanding of what the trees are and how they work, we can see that these moments are opportunities for the forest to showcase the miracle of regeneration, and the many benefits that come with it.
When light and space is made available in the city as well as the forest canopy, it is inevitable that regeneration and the growth of new trees and plants will occur. Disturbances are more than something that forests endure. Ever since there have been forests, there have been fires, windstorms, ice storms, and insect and disease outbreaks. As jarring as they may be to us, forests need disturbances. Forests and the thousands of species that comprise them, have adapted to these disturbances and they are a critical part of how forests change over time, how they become diverse and complex, and how they provide habitat for wildlife.
The miracle of regeneration is the evolutionary response of the forest community to a dynamic world. Light, the currency of the forest, is usually controlled by trees, their broad canopies casting the understory in shade. The death of trees, is a disturbance that creates openings in the forest canopy allowing some of this precious light to reach the forest floor, creating an opportunity for new trees to establish and to grow towards the riches of the canopy and sunlight.
Each tree and plant species in a forest occupies a complex ecological niche. One of the ways that trees’ niches are defined is by the light levels under which they are most competitive. Shade-intolerant species like white birch (Betula papyrifera) and aspen or poplar (Populus nigra) require very large openings, such as those caused by a large-scale or catastrophic disturbances, whereas shade-tolerant species like beech (Fagus), sugar maple (Acer saccharum) and hemlock (Tsuga canadensis) can grow in near or complete shade. Mid-tolerant species like white ash (Fraxinus americana), red oak (Quercus rubra) and yellow birch (Betula alleghaniensis) compete best in mid-sized openings, too small for shade-intolerant trees and too big for slow-growing shade-tolerant trees to be competitive.
Trees are also adapted to occupy a variety of other nitches such as different soil types and depths, on different slopes and aspects. Yellow birch and hemlock seedlings often grow on rotting “nurse logs,” or on the upturned roots of fallen trees. White pine (Pinus strobus) seedlings colonize scarified or disturbed soils, whereas the sugar maple does best with a deep layer of decomposing leaves. Red oak and white ash establish advance regeneration seedlings which may wait in the understory for a decade or more, ready to shoot upwards in the event of a disturbance. Cherries (Prunus), raspberries (Rubus) and blackberries (Rubus) produce seeds that can remain viable but not germinated in forest soils for decades, only sprouting following a wildfire or other disturbance, that leaves a burst of sunlight on the forest floor.
While it is intuitive to think of regeneration as a means to an end. The process by which dead trees are replaced by living trees has tremendous value to the forest community. As a forest regenerates, it passes through many different stages, each of which provides unique habitat; used by wildlife from the insectivorous birds that hunt in canopy gaps, to the pollinators that visit the diversity of herbaceous plants in flower. Each step in this continuum of change is normal, natural and important to a wide range of living things.
Understanding the miracle of regeneration, and the benefits it brings, can change the way that we think about disturbances in the forest. Whether it’s a windstorm or a forest management project. Forests are built on change: every old growth forest was once a young forest and will be once again, and every tree in the woods is the legacy of the death of a tree and the memory of a disturbance.
While it is incredible to witness the resiliency of a forest, how it responds to adversity with regeneration and renewal, this resilience is not limitless. The miracle of regeneration is threatened by invasive plants, pests and pathogens, by over populations of deer, by climate change, by forest fragmentation and by deforestation. In this moment it is critical that we act not just to protect forests but also to protect their ability to regenerate, to adapt, to change, and to remake themselves for the world of the future.
Source
- Tapper, Ethan, Chitchatted County Forester, “Into the Woods: The Miracle of Regeneration”,
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
Trees with Tales
Dove Tree
by Len Phillips
The Tree
Davidia involucrata, commonly called Dove Tree, is a single species with no known living relatives. All other Davidia species are extinct. Another way of saying that Davidia involucrata is a single species is to call it a “monotypic species”. Other monotypic species include Katsura tree Cercidophyllum japonicum, dawn redwood Metasequoia glyptostroboides, and Ginkgo Ginkgo biloba. They are trees that are the only species within their genus. Like the other monotypic species, the Dove Tree has no serious insect or disease problems probably because the pests all died off during the past 60 million years.
The Dove Tree flowers are followed by round, golf ball-sized fruits that are sometimes ridged like a small pumpkin. They are green, becoming speckled with brown and eventually turning purple as they age. They grow on 2 to 3 inch (5 – 8 cm) long red stems. Each fruit contains a single hard "nut" that contains numerous green seeds and become reddish brown as it ripens. The seeds are inside two hard “nuts” shells.
However, there are now two varieties of Davidia selected by mankind and that differ slightly in the characteristics of their leaves. D. involucrata var. involucrata, has leaves with short hairs on the underside and D. involucrata var. vilmoriniana, has hairless leaves. The leaves on the species resemblies those of a linden in appearance and are ovate to heart-shaped and mostly 4 – 8 inches (10–20 cm) long and 3 – 6 inches (7–15 cm) wide. The dark green leaves have a soft white down underneath and are connected to the stem with pink or red petioles. Variable autumn colors range from an undistinguished dull pastel to bright oranges and reds.
The Dove Tree's bark is light gray-brown and smooth with a grayish purple inner bark, later becoming darker, scaly, and orange brown. Buds are scaled, ovoid and pointy in shape, and about one-quarter inch long. As a young tree, it has a pyramidal form that becomes oval to rounded with age. It is a medium sized tree, with a mature height and width of 20–40 feet (6–12 m) with a broad pyramidal habit that becomes rounded as it matures.
Davidia involucrata is most often found growing in private gardens and arboretums where it is usually a focal point. It is seldom if ever, used as a public street tree, but every city should have at least one growing somewhere in the city. The tree is hardy in USDA zones 6 to 8. The Dove Tree is also very difficult to find in nurseries. This tree is a specimen and grows best in full sun or part shade. The soil should be fertile and moist but well-drained. When selecting the site to grow the dove tree, avoid areas with strong winds.
The Tales
The genus Davidia is named for Father Armand David, a French Vincentian missionary and keen naturalist who lived in China in the mid-19th century. Father David first described the tree in 1869 as a single tree found high up on a mountain in central China and he sent dried specimens to Paris for identification. It was several years later when Davidia was identified in fossils from over 60 million years ago when the dinosaurs were roaming the earth. In addition to bringing knowledge of dove trees to the West, Father David also introduced the West to the giant panda (Sauropod melancholic).
Davidia was introduced from China to Europe and North America in 1904, and today it is a popular ornamental tree in parks and larger private gardens even though the dove tree is not well known in the United States. The tree was relatively unknown, even in China, until Chinese leaders saw the tree growing in some gardens in Switzerland and in Washington, D.C. Most trees in cultivation are var. vilmoriniana, which has proved to be much better able to adapt to the climatic conditions in the West. In the United Kingdom, D. involucrata can be seen in many gardens and estates including the Kew Gardens in London.
Davidia involucrata is best known for its very conspicuous flowers which are at their best in late May. They have a ring of very showy white bracts that vary from 3 to 7 inches (8 to 18 cm) long surrounding several tiny red-anthered flowers. A 2008 research paper found evidence to support the idea of bracts serving as protection for pollen from rain and also serving as attractants for pollinators. The white bracts hang in long rows beneath the level branches. On a breezy day, the bracts flutter in the wind like white doves, hence the common name of “Dove Tree” for this tree. Other common names, all in reference to the unique flowers, include “handkerchief tree”, “laundry tree”, and “ghost tree”.
“To my mind Davidia is at once the most interesting and beautiful of all trees of the north-temperate flora…The flowers and their attendant bracts are pendulous on long stalks, and when stirred by the slightest breeze they resemble huge butterflies hovering amongst the trees.”
Ernest Henry Wilson (1876 – 1930) Plant Explorer
Appreciate the Dove Tree for its exceptionally beautiful flower, fruit, leaves, bark, and form while having no disease or insect problems.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
Dove Tree
by Len Phillips
The Tree
Davidia involucrata, commonly called Dove Tree, is a single species with no known living relatives. All other Davidia species are extinct. Another way of saying that Davidia involucrata is a single species is to call it a “monotypic species”. Other monotypic species include Katsura tree Cercidophyllum japonicum, dawn redwood Metasequoia glyptostroboides, and Ginkgo Ginkgo biloba. They are trees that are the only species within their genus. Like the other monotypic species, the Dove Tree has no serious insect or disease problems probably because the pests all died off during the past 60 million years.
The Dove Tree flowers are followed by round, golf ball-sized fruits that are sometimes ridged like a small pumpkin. They are green, becoming speckled with brown and eventually turning purple as they age. They grow on 2 to 3 inch (5 – 8 cm) long red stems. Each fruit contains a single hard "nut" that contains numerous green seeds and become reddish brown as it ripens. The seeds are inside two hard “nuts” shells.
However, there are now two varieties of Davidia selected by mankind and that differ slightly in the characteristics of their leaves. D. involucrata var. involucrata, has leaves with short hairs on the underside and D. involucrata var. vilmoriniana, has hairless leaves. The leaves on the species resemblies those of a linden in appearance and are ovate to heart-shaped and mostly 4 – 8 inches (10–20 cm) long and 3 – 6 inches (7–15 cm) wide. The dark green leaves have a soft white down underneath and are connected to the stem with pink or red petioles. Variable autumn colors range from an undistinguished dull pastel to bright oranges and reds.
The Dove Tree's bark is light gray-brown and smooth with a grayish purple inner bark, later becoming darker, scaly, and orange brown. Buds are scaled, ovoid and pointy in shape, and about one-quarter inch long. As a young tree, it has a pyramidal form that becomes oval to rounded with age. It is a medium sized tree, with a mature height and width of 20–40 feet (6–12 m) with a broad pyramidal habit that becomes rounded as it matures.
Davidia involucrata is most often found growing in private gardens and arboretums where it is usually a focal point. It is seldom if ever, used as a public street tree, but every city should have at least one growing somewhere in the city. The tree is hardy in USDA zones 6 to 8. The Dove Tree is also very difficult to find in nurseries. This tree is a specimen and grows best in full sun or part shade. The soil should be fertile and moist but well-drained. When selecting the site to grow the dove tree, avoid areas with strong winds.
The Tales
The genus Davidia is named for Father Armand David, a French Vincentian missionary and keen naturalist who lived in China in the mid-19th century. Father David first described the tree in 1869 as a single tree found high up on a mountain in central China and he sent dried specimens to Paris for identification. It was several years later when Davidia was identified in fossils from over 60 million years ago when the dinosaurs were roaming the earth. In addition to bringing knowledge of dove trees to the West, Father David also introduced the West to the giant panda (Sauropod melancholic).
Davidia was introduced from China to Europe and North America in 1904, and today it is a popular ornamental tree in parks and larger private gardens even though the dove tree is not well known in the United States. The tree was relatively unknown, even in China, until Chinese leaders saw the tree growing in some gardens in Switzerland and in Washington, D.C. Most trees in cultivation are var. vilmoriniana, which has proved to be much better able to adapt to the climatic conditions in the West. In the United Kingdom, D. involucrata can be seen in many gardens and estates including the Kew Gardens in London.
Davidia involucrata is best known for its very conspicuous flowers which are at their best in late May. They have a ring of very showy white bracts that vary from 3 to 7 inches (8 to 18 cm) long surrounding several tiny red-anthered flowers. A 2008 research paper found evidence to support the idea of bracts serving as protection for pollen from rain and also serving as attractants for pollinators. The white bracts hang in long rows beneath the level branches. On a breezy day, the bracts flutter in the wind like white doves, hence the common name of “Dove Tree” for this tree. Other common names, all in reference to the unique flowers, include “handkerchief tree”, “laundry tree”, and “ghost tree”.
“To my mind Davidia is at once the most interesting and beautiful of all trees of the north-temperate flora…The flowers and their attendant bracts are pendulous on long stalks, and when stirred by the slightest breeze they resemble huge butterflies hovering amongst the trees.”
Ernest Henry Wilson (1876 – 1930) Plant Explorer
Appreciate the Dove Tree for its exceptionally beautiful flower, fruit, leaves, bark, and form while having no disease or insect problems.
Sources
- Arnold Arboretum, “Bulletin of Popular Information, Series 3 Vol..V No. 7”, May 29, 1931
- Dirr, Michael A. and Keith S. Warren, “The Tree Book”, Timber Press, 2019.
- Missouri Botanical Garden, “Davidia involucrata”, Plant Finder
- Plant Explorer, “Ernest Henry Wilson”, Feature Article, 2017
- Kew Gardens, “Davidia involucrata”, 6 June 2017
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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 Summer of 2022
Edited by Len Phillips
The summer of 2022 was marked with heat waves, drought, wildfires and floods which have destroyed vast areas of vegetation and a very large number of trees especially in our cities and in the western states of the U.S. Although the heat from wildfires is different than heat in an urban environment, the impact of heat on vegetation everywhere results in a problem of stifled growth. This article describes the impact of weather extremes on trees in the city and highlights the differences in behavior of trees located in parks compared to trees along the streets of our cities.
Trees bring many benefits to their environment, including a real refreshment to urban open spaces. It is critical that given these surroundings, trees in the city should not be distressed due to lack of water or subjected to temperatures to which they are not adapted. The arborist must assist the trees dealing with these environmental extremes.
In the summer months, the stresses have accumulated because of record high temperatures and very low rainfall around the globe. A recent study looked at four dense urban areas in New York, London, Paris and Lyon, France. For each of these four sites, a comparison between 2021 and 2022 determined the effect on the tree patrimony and the effect on urban parks located in London, England and Lyon, France.
The comparison began with a sensitivity analysis of the trees in these four cities. The analysis compared the location of the trees, their age, their species, etc. The first step consisted of evaluating the level of drought stress on each tree and comparing the changes between 2021 and 2022.
The water stress was found to be much greater in 2022 than in 2021. It is interesting to note that street trees are the first to suffer from water stress. Resilience is better in wooded parks, even if these trees also showed a certain water deficit.
The study went on to evaluate the canopy, taking into account different levels of canopy quality and density. The following results were obtained using satellite data:
These results confirm the diagnosis that can be seen in the field on a number of trees with shriveled leaves. They also lead us to think about important questions for development projects and re-vegetation strategies:
The sensitivity analysis according to the species provides very important additional information, which can be presented later. In addition to the diagnostic aspect that was just illustrated, this approach also allows dynamic monitoring of the behavior of trees over the weeks, opening possibilities for preventive management of wooded areas.
Source
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
Edited by Len Phillips
The summer of 2022 was marked with heat waves, drought, wildfires and floods which have destroyed vast areas of vegetation and a very large number of trees especially in our cities and in the western states of the U.S. Although the heat from wildfires is different than heat in an urban environment, the impact of heat on vegetation everywhere results in a problem of stifled growth. This article describes the impact of weather extremes on trees in the city and highlights the differences in behavior of trees located in parks compared to trees along the streets of our cities.
Trees bring many benefits to their environment, including a real refreshment to urban open spaces. It is critical that given these surroundings, trees in the city should not be distressed due to lack of water or subjected to temperatures to which they are not adapted. The arborist must assist the trees dealing with these environmental extremes.
In the summer months, the stresses have accumulated because of record high temperatures and very low rainfall around the globe. A recent study looked at four dense urban areas in New York, London, Paris and Lyon, France. For each of these four sites, a comparison between 2021 and 2022 determined the effect on the tree patrimony and the effect on urban parks located in London, England and Lyon, France.
The comparison began with a sensitivity analysis of the trees in these four cities. The analysis compared the location of the trees, their age, their species, etc. The first step consisted of evaluating the level of drought stress on each tree and comparing the changes between 2021 and 2022.
The water stress was found to be much greater in 2022 than in 2021. It is interesting to note that street trees are the first to suffer from water stress. Resilience is better in wooded parks, even if these trees also showed a certain water deficit.
The study went on to evaluate the canopy, taking into account different levels of canopy quality and density. The following results were obtained using satellite data:
- The canopy surface is a little lower in 2022 than it was in 2021. Tree growth was disrupted by the very early heat waves.
- The tree quality changed significantly because of the heat.
- The tree density and level of hydration also changed all the result of climatic conditions.
These results confirm the diagnosis that can be seen in the field on a number of trees with shriveled leaves. They also lead us to think about important questions for development projects and re-vegetation strategies:
- Street trees in pits, even large ones, are under increased stress. Access to water resources is more limited for them. They also suffer from the solar fluxes reflected by the mineral soil that surrounds them and do not benefit from the support of their conveners.
- Groups of trees display a much better resistance to stress because the trees benefited from the protection of their neighbors. Peripheral canopies are often more impacted.
The sensitivity analysis according to the species provides very important additional information, which can be presented later. In addition to the diagnostic aspect that was just illustrated, this approach also allows dynamic monitoring of the behavior of trees over the weeks, opening possibilities for preventive management of wooded areas.
Source
- Eric Larrey, “Construction 21 International”, August 21, 2022.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
New Trees for Our Cities
Edited by Len Phillips
Last summer nurseries were evaluating some new and cool looking introductions of trees for our cities. If you are interested in purchasing any of these trees for spring delivery, you better place your order NOW!! The nursery industry is anticipating huge demand for trees this spring and there will probably be shortages of the trees you want.
While you might think all the best new trees become available in the spring, they are available in autumn and winter. That is when they are being dug for winter storage and evaluated for their appearance after a long hot and humid summer. The best-looking trees are the ones being named as new selections for spring sales at the nurseries. Here is a list of some of the newest and coolest introductions from a very large nursery that sells trees all over the world. If any of these are of interest to you, you better place your order soon. (Click on the titles for a photo and more information about the tree.)
Autumn Treasure® Hophornbeam, Ostyra virginiana ‘JFS-KW5’
Tailor-made for city living, the predictably upright and narrow form of this American Hophornbeam was selected for suitability as a street tree and as a medium size shade tree. Upright and pyramidal in shape, with a strong central leader and sturdy branch structure, it brings uniformity to a rather variable species. Chains of papery, hop-like catkins that appear among the dark green leaves in late summer are a distinctive, ornamental feature. Though the species typically holds brown leaves through the winter months, the foliage of this stately cultivar turns golden yellow before dropping cleanly and completely in autumn. Typically rounded in form, this cultivar of a North American native tree that matures at a height and spread of 40’ x 20’ (12 x 6m) is hardy through USDA Zone 4.
Chastity® Pear, Pyrus x tripodal ‘NCPX2' PP 30788
Prolific white blooms of spring are followed by glossy dark green foliage that presents a kaleidoscopic medley of red, orange, yellow and purple colors in autumn. This fire blight-resistant hybrid is a highly infertile, induced diploid hybrid specifically bred by Dr. Tom Ranee of North Carolina State University to prevent weediness and to be nearly fruitless. The open branch angles contribute to its storm-resistant structure and broadly symmetrical and pyramidal form. Chastity® Pear delivers the beauty, durability and adaptability of flowering pear cultivars without their negative characteristics. Chastity® Pear reaches a height and spread of approximately 35‘x 25’ (11 x 7.5m) and it is hardy through USDA Hardiness Zone 5.
American Dream® Oak, Quercus bicolor 'JFS-KW12’ PP23632
This selection is a tough and adaptable North American native oak that offers the species’ drought tolerance and it has an ability to thrive in poorly drained sites. Plus, it has superior resistance to anthracnose and powdery mildew. Its large, lustrous, deep green leaves are thick and glossy, with wavy margins. After turning buttery yellow in autumn, they turn to a rich tawny brown and remain on the tree late into the season. A vigorous grower, American Dream® Oak develops a symmetrical, broadly pyramidal canopy of good density. It reaches a mature height and spread of approximately 50’ x 40’ (16 x 12m). Its hardiness is through USDA Zone 4
Summer Elixir™ Elm, Ulmus chenmoui ‘JAB Morton’
This elm is smaller in stature than most other elms. It is a compact, nicely formed tree that is a good fit for many of today’s scaled-down landscape settings. While it is vase-shaped in youth, it develops a rounded shape as it matures to a height and spread of 35’ x 30’ (11 x 9m). Summer Elixir is tolerant of Dutch elm disease and also resists the feeding of elm leaf beetles. Its stand-out characteristics include a relatively small mature form. Its hardiness is through USDA Zone 5.
Greenstone® Elm, Ulmus davidiana ‘JFS KW2UD’
Grown from seed collected from cold hardy native trees at the northern edge of its native range in China, Greenstone® Elm is well suited for cold and difficult growing conditions. It is tolerant of both Dutch elm disease and phloem necrosis. It was selected as an attractive and look-alike of the American elm. Through years of testing, this vigorous grower has proven to be the top performer among trees grown from seed collected at the Northern edge of its native range in China. Its strong branches with open angles develop into an upright vase shape resembling that of the classic American elm. The rich medium green leaves have a yellow autumn color fall cleanly to reveal a winter silhouette that recalls the classic upright vase shape of the American elm (Ulmus americana). The mature size of this new tree is approximately 60’ x 40’ (18 x 12m high x wide). Its USDA Hardiness Zone is 4.
Zileration™ Zelkova, Zelkova serrata ‘JFS KW4ZS’ P.A.F.
This Zelkova has clean, dark green summer foliage. It also has symmetrical branching and a compact, dense canopy that make this new cultivar a standout among Zelkova cultivars. The unusually compact structure and the intermediate size of this upright and vase-shaped tree is a better fit for many intimate landscape settings than the typically larger cultivars of the Zelkova species that can be found on our streets. Maturing to a height and spread of approximately 30’ x 25’ (9 x 7.5m), it offers year-round appeal that includes handsome winter structure. The fine-textured dark green foliage turns rusty orange in autumn. Its USDA Zone 5 hardiness is typical of the species.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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
Last summer nurseries were evaluating some new and cool looking introductions of trees for our cities. If you are interested in purchasing any of these trees for spring delivery, you better place your order NOW!! The nursery industry is anticipating huge demand for trees this spring and there will probably be shortages of the trees you want.
While you might think all the best new trees become available in the spring, they are available in autumn and winter. That is when they are being dug for winter storage and evaluated for their appearance after a long hot and humid summer. The best-looking trees are the ones being named as new selections for spring sales at the nurseries. Here is a list of some of the newest and coolest introductions from a very large nursery that sells trees all over the world. If any of these are of interest to you, you better place your order soon. (Click on the titles for a photo and more information about the tree.)
Autumn Treasure® Hophornbeam, Ostyra virginiana ‘JFS-KW5’
Tailor-made for city living, the predictably upright and narrow form of this American Hophornbeam was selected for suitability as a street tree and as a medium size shade tree. Upright and pyramidal in shape, with a strong central leader and sturdy branch structure, it brings uniformity to a rather variable species. Chains of papery, hop-like catkins that appear among the dark green leaves in late summer are a distinctive, ornamental feature. Though the species typically holds brown leaves through the winter months, the foliage of this stately cultivar turns golden yellow before dropping cleanly and completely in autumn. Typically rounded in form, this cultivar of a North American native tree that matures at a height and spread of 40’ x 20’ (12 x 6m) is hardy through USDA Zone 4.
Chastity® Pear, Pyrus x tripodal ‘NCPX2' PP 30788
Prolific white blooms of spring are followed by glossy dark green foliage that presents a kaleidoscopic medley of red, orange, yellow and purple colors in autumn. This fire blight-resistant hybrid is a highly infertile, induced diploid hybrid specifically bred by Dr. Tom Ranee of North Carolina State University to prevent weediness and to be nearly fruitless. The open branch angles contribute to its storm-resistant structure and broadly symmetrical and pyramidal form. Chastity® Pear delivers the beauty, durability and adaptability of flowering pear cultivars without their negative characteristics. Chastity® Pear reaches a height and spread of approximately 35‘x 25’ (11 x 7.5m) and it is hardy through USDA Hardiness Zone 5.
American Dream® Oak, Quercus bicolor 'JFS-KW12’ PP23632
This selection is a tough and adaptable North American native oak that offers the species’ drought tolerance and it has an ability to thrive in poorly drained sites. Plus, it has superior resistance to anthracnose and powdery mildew. Its large, lustrous, deep green leaves are thick and glossy, with wavy margins. After turning buttery yellow in autumn, they turn to a rich tawny brown and remain on the tree late into the season. A vigorous grower, American Dream® Oak develops a symmetrical, broadly pyramidal canopy of good density. It reaches a mature height and spread of approximately 50’ x 40’ (16 x 12m). Its hardiness is through USDA Zone 4
Summer Elixir™ Elm, Ulmus chenmoui ‘JAB Morton’
This elm is smaller in stature than most other elms. It is a compact, nicely formed tree that is a good fit for many of today’s scaled-down landscape settings. While it is vase-shaped in youth, it develops a rounded shape as it matures to a height and spread of 35’ x 30’ (11 x 9m). Summer Elixir is tolerant of Dutch elm disease and also resists the feeding of elm leaf beetles. Its stand-out characteristics include a relatively small mature form. Its hardiness is through USDA Zone 5.
Greenstone® Elm, Ulmus davidiana ‘JFS KW2UD’
Grown from seed collected from cold hardy native trees at the northern edge of its native range in China, Greenstone® Elm is well suited for cold and difficult growing conditions. It is tolerant of both Dutch elm disease and phloem necrosis. It was selected as an attractive and look-alike of the American elm. Through years of testing, this vigorous grower has proven to be the top performer among trees grown from seed collected at the Northern edge of its native range in China. Its strong branches with open angles develop into an upright vase shape resembling that of the classic American elm. The rich medium green leaves have a yellow autumn color fall cleanly to reveal a winter silhouette that recalls the classic upright vase shape of the American elm (Ulmus americana). The mature size of this new tree is approximately 60’ x 40’ (18 x 12m high x wide). Its USDA Hardiness Zone is 4.
Zileration™ Zelkova, Zelkova serrata ‘JFS KW4ZS’ P.A.F.
This Zelkova has clean, dark green summer foliage. It also has symmetrical branching and a compact, dense canopy that make this new cultivar a standout among Zelkova cultivars. The unusually compact structure and the intermediate size of this upright and vase-shaped tree is a better fit for many intimate landscape settings than the typically larger cultivars of the Zelkova species that can be found on our streets. Maturing to a height and spread of approximately 30’ x 25’ (9 x 7.5m), it offers year-round appeal that includes handsome winter structure. The fine-textured dark green foliage turns rusty orange in autumn. Its USDA Zone 5 hardiness is typical of the species.
Sources
- Nancy Buley, “Stock Available & Nursery News”, courtesy of J. Frank Schmidt & Son Co.
- “Reference Guide”, J. Frank Schmidt & Son, 2022.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
Horatio Hollis Hunnewell by Len Phillips
Horatio Hollis Hunnewell 1810 – 1902 was a very prominent horticulturist, tree lover and amateur botanist in the United States during the nineteenth century. He was involved with collecting trees, supporting the beginnings of the Arnold Arboretum, creating his own pinetum and developing a large topiary garden of full-size evergreen trees in Wellesley, Massachusetts.
Hollis was an American railroad financier and philanthropist. He earned a large fortune as a partner in the private banking firm of Welles & Co. located in Paris, France. The bank was controlled by his in-laws, the Welles family, which specialized in financing trade between the US and France.
Both the Town of Wellesley (founded 1881) and Wellesley College (chartered 1870) are named after the Hunnewell estate, "Wellesley". It was named for the family of his wife, Isabella Pratt Welles, whom he married in 1835. The very large tract of land owned by the H. H. Hunnewell estate includes a prominent 1851 mansion designed by Arthur Gilman with an attached conservatory and gatehouses at each entrance to the estate. In 1865 and 1866, architect, Gridley J.F. Bryant, designed the estate land to include the main mansion and a complex of large homes for the Hunnewell family children. The specialty greenhouses for Hollis, all of which are still standing and are full of everything from seedlings to full size trees and rhododendrons as well as a greenhouse dedicated to growing plants for the estate grounds. Architect Bryant also set aside land for the future Wellesley College and the pinetum. Near the main estate is the building containing the headquarters of the Massachusetts Horticultural Society's Elm Bank Headquarters. Behind this building is a certified Flower Field Trial Garden. The Horticultural Society's office is in a mansion originally built for one of Hollis's children.
Hollis had a lifelong love of nature and gardening. He planted the very first topiary garden in America at his estate. He referred to it as the Italian Garden and it was ideally situated along the shores of Lake Waban near his house. The topiary garden consists of full-size white pine trees that have been shaped in various topiary forms. The trees line the steep bank around the Lake. Most of the trees are still there to this day and they all receive an annual trimming to maintain their topiary features. The trimming crew hauls long wood ladders which rest on the branches of the trees being trimmed.
Hollis also developed a pinetum of 325 specimen conifers. Each evergreen tree was grown from seed
by Hollis before they were transplanted and labeled in the pinetum. His family continues to add new evergreens as they become available, and they replace the older specimens when they die. This author measured many of the Wellesley pinetum trees so they could be added to the American Forests list of Champion Trees in North America. Hollis also funded the conifer collection at the Arnold Arboretum in Boston.
Practicing horticulture for nearly six decades on his estate in Wellesley, Hollis was one of the first people to cultivate and popularize rhododendrons in the United States. Rhododendron hunnewellianum was introduced in 1908 as a distinct species on account of its stiff, very narrow leaves, that are gray, white beneath.
Today the Hunnewell family continues to be known as ardent patrons of horticulture and botany in Massachusetts. Very large individual specimens of Rhododendron hunnewellianum can be found scattered all around the Hunnewell estate.
H. H. Hunnewell made a donation that supported Asa Gray as he revised, expanded and completed his Flora of North America book in 1873. In 1892 in one of his last, most generous donations, Hollis provided funds to build the Arnold Arboretum's administration building, now known as the “Hunnewell Building”. Most important however, was the fondness of trees and shrubs that Hollis endowed in his children. For example, just a couple of years ago, one of his granddaughters funded the construction of a footbridge over the Charles River linking a landscaped walking trail from Wellesley to the neighboring City of Newton.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
Horatio Hollis Hunnewell 1810 – 1902 was a very prominent horticulturist, tree lover and amateur botanist in the United States during the nineteenth century. He was involved with collecting trees, supporting the beginnings of the Arnold Arboretum, creating his own pinetum and developing a large topiary garden of full-size evergreen trees in Wellesley, Massachusetts.
Hollis was an American railroad financier and philanthropist. He earned a large fortune as a partner in the private banking firm of Welles & Co. located in Paris, France. The bank was controlled by his in-laws, the Welles family, which specialized in financing trade between the US and France.
Both the Town of Wellesley (founded 1881) and Wellesley College (chartered 1870) are named after the Hunnewell estate, "Wellesley". It was named for the family of his wife, Isabella Pratt Welles, whom he married in 1835. The very large tract of land owned by the H. H. Hunnewell estate includes a prominent 1851 mansion designed by Arthur Gilman with an attached conservatory and gatehouses at each entrance to the estate. In 1865 and 1866, architect, Gridley J.F. Bryant, designed the estate land to include the main mansion and a complex of large homes for the Hunnewell family children. The specialty greenhouses for Hollis, all of which are still standing and are full of everything from seedlings to full size trees and rhododendrons as well as a greenhouse dedicated to growing plants for the estate grounds. Architect Bryant also set aside land for the future Wellesley College and the pinetum. Near the main estate is the building containing the headquarters of the Massachusetts Horticultural Society's Elm Bank Headquarters. Behind this building is a certified Flower Field Trial Garden. The Horticultural Society's office is in a mansion originally built for one of Hollis's children.
Hollis had a lifelong love of nature and gardening. He planted the very first topiary garden in America at his estate. He referred to it as the Italian Garden and it was ideally situated along the shores of Lake Waban near his house. The topiary garden consists of full-size white pine trees that have been shaped in various topiary forms. The trees line the steep bank around the Lake. Most of the trees are still there to this day and they all receive an annual trimming to maintain their topiary features. The trimming crew hauls long wood ladders which rest on the branches of the trees being trimmed.
Hollis also developed a pinetum of 325 specimen conifers. Each evergreen tree was grown from seed
by Hollis before they were transplanted and labeled in the pinetum. His family continues to add new evergreens as they become available, and they replace the older specimens when they die. This author measured many of the Wellesley pinetum trees so they could be added to the American Forests list of Champion Trees in North America. Hollis also funded the conifer collection at the Arnold Arboretum in Boston.
Practicing horticulture for nearly six decades on his estate in Wellesley, Hollis was one of the first people to cultivate and popularize rhododendrons in the United States. Rhododendron hunnewellianum was introduced in 1908 as a distinct species on account of its stiff, very narrow leaves, that are gray, white beneath.
Today the Hunnewell family continues to be known as ardent patrons of horticulture and botany in Massachusetts. Very large individual specimens of Rhododendron hunnewellianum can be found scattered all around the Hunnewell estate.
H. H. Hunnewell made a donation that supported Asa Gray as he revised, expanded and completed his Flora of North America book in 1873. In 1892 in one of his last, most generous donations, Hollis provided funds to build the Arnold Arboretum's administration building, now known as the “Hunnewell Building”. Most important however, was the fondness of trees and shrubs that Hollis endowed in his children. For example, just a couple of years ago, one of his granddaughters funded the construction of a footbridge over the Charles River linking a landscaped walking trail from Wellesley to the neighboring City of Newton.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
The Best of the Best New Trees for the Future
Edited by Len Phillips
According to the biggest and best nursery industry trade show, the following trees have been selected as the best of the best new trees for the future. These trees have been bred to tolerate global warming while having the award-winning features of beauty and tolerance to most soils and survival in the harsh conditions for growth in our cities.
Acer rubrum ‘Frank Jr.’Redpointe® Maple
A superior selection of the widely planted maple species, Redpointe® Maple is distinctive for its rich, dark green, heat-tolerant summer foliage that turns to brilliant red in autumn. Its upright, broadly pyramidal form and adaptability to urban growing conditions make it a natural choice for street tree plantings and cityscapes. Ease of care in the nursery and in the landscape, plus tolerance to heat, cold, drought and varied soils (including those of higher pH levels) have helped it to become a best-selling tree since its introduction in 2006. Height and spread are approximately 45’ x 30’ after 30 years in an average urban landscape setting. A straight and dominant central leader results in strong branch angles that make it easier to grow
Acer rubrum 'JFS-KW78' PP 25301 Armstrong Gold® Maple
Slender spires of rich green leaves turn to bright golden orange in autumn. Narrow, tightly columnar form brings beauty, utility, and a strongly vertical design element to streetscapes and landscapes where space is at a premium. A good choice for narrow planting spaces, it reaches a height and spread of 40’ x 12’. Selected from an evaluation of hundreds of seedlings, its brighter foliage color, greater foliage density and compact, less leggy growth habit, recommend Armstrong Gold® Maple over its successful and widely planted parent, the Armstrong Maple. Armstrong Gold®'s always bright autumn color ranges from bright orange to golden orange. Hardiness is USDA Zone 4.
Acer truncatum x A. platanoides ‘JFS-KW187’ Urban Sunset® Maple
This natural born street tree was selected from a 30+ year effort to combine the best characteristics of Asian and European maple species. Dark green leaves of this heat and drought tolerant tree are glossy and tatter-resistant, exploding with bright red to deep red tones in autumn. Vigorous and upright growing with a strong central leader, Urban Sunset® Maple calipers well and develops a uniformly branched compact canopy, easy to grow with minimal pruning, remaining compact and narrow as it develops an ideal street tree form. It produces very few seeds and is pest and disease resistant. Hardy through USDA Zone 5, it matures to a height of approximately 35 feet and spread of 20 feet.
Malus ‘JFS-KW207’ PP 27954 Sparkling Sprite® Crabapple
Pink buds of Sparkling Sprite® Crabapple open to fragrant, pink-tinged white flowers that smother its densely branched, rounded head. The summer foliage of this petite top-grafted tree is especially clean, bright green and disease resistant. The show goes on well into winter, when an abundant crop of tiny I/4”apples” turn from golden yellow to orange and attract birds to your garden. Hardy through USDA Zone 4. Growing to a height and spread of approximately 12’ x 12’, it is perfectly rounded compact canopy maintains a year-round, formal, topiary-like shape with little to no pruning.
Nyssa sylvatica ‘David Odom’ Afterburner® Tupelo
Uniquely upright branch structure, symmetrical form, and a rocket-straight, dominant central leader delight growers, specifiers and urban foresters who are frustrated with the irregular, floppy branch habit of typical seedlings of this popular North American native tree. Glossy, clean, deep green summer foliage is highly resistant to foliage diseases typical of the species. Hardy through USDA Zone 5 and growing to a height and spread of approximately 12’ x 12’ All color begins to develop mid-season and shines bright red after other trees of the species have defoliated. This means delivering an extra shot of red-hot color reminiscent of red-hot exhaust produced by the afterburner of a super-fast jet plane.
Styrax japonicus ‘JFS 6SJ’ P.A.F. Nightfall™ Snowbell
The newly introduced Nightfall™ Snowbell, is a fabulous and successful tree that produces the white buds of late spring's bell shaped flowers that open to creamy white. Nightfall™ Snowbell was selected from 12 amazing plants and was judged worthy of sharing with garden centers and with the horticultural community at large. It grows 8 feet tall and 6 feet wide.
Zelkova serrata ‘JFS-KW1’ PP 20996 City Sprite® Zelkova
Urban foresters and utility companies appreciate the compact, mannerly growth habit of this petite city tree. Short internodes contribute to its compact, dense, and semi-dwarf form, resulting in the perfect little tree for tight urban spaces and a low maintenance tree to grow under the utility wires. Oval to vase-shaped, it grows to a height of approximately 24 feet with a spread of about 18 feet. Fine textured foliage is brighter green in summer than the leaves of typical Zelkova and turns yellow in autumn. Hardiness is USDA Zone 5. Embraced by urban foresters and landscape designers, it is on its way to becoming a very popular tree.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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
According to the biggest and best nursery industry trade show, the following trees have been selected as the best of the best new trees for the future. These trees have been bred to tolerate global warming while having the award-winning features of beauty and tolerance to most soils and survival in the harsh conditions for growth in our cities.
Acer rubrum ‘Frank Jr.’Redpointe® Maple
A superior selection of the widely planted maple species, Redpointe® Maple is distinctive for its rich, dark green, heat-tolerant summer foliage that turns to brilliant red in autumn. Its upright, broadly pyramidal form and adaptability to urban growing conditions make it a natural choice for street tree plantings and cityscapes. Ease of care in the nursery and in the landscape, plus tolerance to heat, cold, drought and varied soils (including those of higher pH levels) have helped it to become a best-selling tree since its introduction in 2006. Height and spread are approximately 45’ x 30’ after 30 years in an average urban landscape setting. A straight and dominant central leader results in strong branch angles that make it easier to grow
Acer rubrum 'JFS-KW78' PP 25301 Armstrong Gold® Maple
Slender spires of rich green leaves turn to bright golden orange in autumn. Narrow, tightly columnar form brings beauty, utility, and a strongly vertical design element to streetscapes and landscapes where space is at a premium. A good choice for narrow planting spaces, it reaches a height and spread of 40’ x 12’. Selected from an evaluation of hundreds of seedlings, its brighter foliage color, greater foliage density and compact, less leggy growth habit, recommend Armstrong Gold® Maple over its successful and widely planted parent, the Armstrong Maple. Armstrong Gold®'s always bright autumn color ranges from bright orange to golden orange. Hardiness is USDA Zone 4.
Acer truncatum x A. platanoides ‘JFS-KW187’ Urban Sunset® Maple
This natural born street tree was selected from a 30+ year effort to combine the best characteristics of Asian and European maple species. Dark green leaves of this heat and drought tolerant tree are glossy and tatter-resistant, exploding with bright red to deep red tones in autumn. Vigorous and upright growing with a strong central leader, Urban Sunset® Maple calipers well and develops a uniformly branched compact canopy, easy to grow with minimal pruning, remaining compact and narrow as it develops an ideal street tree form. It produces very few seeds and is pest and disease resistant. Hardy through USDA Zone 5, it matures to a height of approximately 35 feet and spread of 20 feet.
Malus ‘JFS-KW207’ PP 27954 Sparkling Sprite® Crabapple
Pink buds of Sparkling Sprite® Crabapple open to fragrant, pink-tinged white flowers that smother its densely branched, rounded head. The summer foliage of this petite top-grafted tree is especially clean, bright green and disease resistant. The show goes on well into winter, when an abundant crop of tiny I/4”apples” turn from golden yellow to orange and attract birds to your garden. Hardy through USDA Zone 4. Growing to a height and spread of approximately 12’ x 12’, it is perfectly rounded compact canopy maintains a year-round, formal, topiary-like shape with little to no pruning.
Nyssa sylvatica ‘David Odom’ Afterburner® Tupelo
Uniquely upright branch structure, symmetrical form, and a rocket-straight, dominant central leader delight growers, specifiers and urban foresters who are frustrated with the irregular, floppy branch habit of typical seedlings of this popular North American native tree. Glossy, clean, deep green summer foliage is highly resistant to foliage diseases typical of the species. Hardy through USDA Zone 5 and growing to a height and spread of approximately 12’ x 12’ All color begins to develop mid-season and shines bright red after other trees of the species have defoliated. This means delivering an extra shot of red-hot color reminiscent of red-hot exhaust produced by the afterburner of a super-fast jet plane.
Styrax japonicus ‘JFS 6SJ’ P.A.F. Nightfall™ Snowbell
The newly introduced Nightfall™ Snowbell, is a fabulous and successful tree that produces the white buds of late spring's bell shaped flowers that open to creamy white. Nightfall™ Snowbell was selected from 12 amazing plants and was judged worthy of sharing with garden centers and with the horticultural community at large. It grows 8 feet tall and 6 feet wide.
Zelkova serrata ‘JFS-KW1’ PP 20996 City Sprite® Zelkova
Urban foresters and utility companies appreciate the compact, mannerly growth habit of this petite city tree. Short internodes contribute to its compact, dense, and semi-dwarf form, resulting in the perfect little tree for tight urban spaces and a low maintenance tree to grow under the utility wires. Oval to vase-shaped, it grows to a height of approximately 24 feet with a spread of about 18 feet. Fine textured foliage is brighter green in summer than the leaves of typical Zelkova and turns yellow in autumn. Hardiness is USDA Zone 5. Embraced by urban foresters and landscape designers, it is on its way to becoming a very popular tree.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
Mulch Myths
By Butch Ragland, edited by RW Gibney
Lush meadows and healthy forests require soil started from mulch, also known as that fresh layer of organic matter (dead grass and leaves) on the surface. Under that fresh layer of mulch is just-started compost (decaying mulch), followed by finished compost a few inches below the surface. Below all the compost comes the healthy parent soil with compost mixed throughout. This soil is ideal for healthy trees. I call this the Natural Process. In one gram of healthy soil there are as many as 3 billion organisms plus a whole range of interactions between all these organisms.
The Nitrogen-Loss Myth
Have you heard that compost uses so much soil nitrogen that you should add fertilizer to the compost pile to make it work better? The reality is that compost and mulch do not cause nitrogen to be depleted from the soil, if they are placed on top of the soil and are not incorporated into the soil by tilling. The idea that mulch causes nitrogen loss is a myth.
A host of organisms, including bacteria, worms, and fungi, break down the organic matter in mulch and compost and begin to change it into a form that will enhance tree growth by the humidification process and produce a rich soil. Research shows that this process utilizes nitrogen from air above, not the soil below.
Nitrogen is essential for making proteins in the soil. This nitrogen is stored within microorganisms' cellular structures found in the soil and in organic matter. It has been said that 75% of the nutrients in soil are stored in the microorganisms. Because of this, the nitrogen, along with many other trace minerals, cannot be leached from the soil by spring snow melt or summer irrigation. A plant’s roots will feed on the microorganism-stored nitrogen.
The Great Planting Hole Myth
University of California researchers found that putting any organic material into a planting hole caused a first-year reduction in growth of the tree planted in it. After the tree became established it recovered and grew normally. The researchers found that removing the soil from the hole, planting the tree and then putting back the removed soil around the roots gave the best results. No additional organic supplementation into the hole itself is necessary.
Arborists know that soil is a very poor container-growing medium because it is a living organism. Container-growers had to devise a method to grow trees in pots; hence a soil-less mix of sand and bark was developed. This soil-less mix is dead soil, microorganism-wise. It holds the plant upright while the growers deliver the nutrients and water that will encourage trees to grow. The techniques used to grow trees in a container do not transfer to the soil, however. This is when it makes sense to wash all the soil off the roots and plant the tree, bare root.
Grit, rock, perlite, vermiculite and all of the things used to create good drainage, moisture-holding properties, etc. and found in the container grown tree, are useless in your tree planting pit and in fact interfere with the natural process. If the soil you are planting in is surrounded by meadows or forest, it will grow trees. Since this is often impossible along city streets, rubble and poor soils such as clay and sandy soil must be changed, but the arborist cannot change them by amending the soil with magic ingredients. The poor soils must be changed by removing 75% of the existing material throughout the entire area available for the mature tree root space and mixing the remaining soil with loam and organic material such as compost to provide permeability and food for microorganisms.
Mulch makes the Soil Acidic Myth
The importance of regulating pH in the tree planting pit is another myth. Get a soil sample and send it to your local extension office or some of the larger retail nurseries, for testing. When you receive the results, base your tree selection on the test’s outcome. You cannot change the pH of your soil in any meaningful way. Soil sampling evolved out of farmers needing to control pH as they grow crops in rows. In that situation, the farmer, with the help of a tractor, has destroyed the structure of his field, and must regulate the pH and nutrient levels every year for as long as the soil is used for crops. pH adjustment is possible for turf as the root zone is in the upper 2” of soil where soil amendments are most effective.
Trees however are a different story. This is because the pH of your particular soil type will not easily move from acidic or basic toward a neutral pH, at least in the root zone, where it counts for your trees. Mulch will move your soil pH slightly toward neutral, but only at the soil/mulch interface. It is prudent to test your mulch or receive a certification of testing from the mulch producer. This should show a pH of 6.0 – 7.2 and balanced nutrient levels (NPK) in low ranges.
The Tilling Myth
How did trees grow before the rototiller? Tilling (turning the soil over but leaving it in place) and double digging are not good practices for growing trees. The double digging process requires digging a trench across the tree planting pit, then digging a second, similar-size trench next to the first, this time placing the excavated soil from the second trench mixed with organic matter into the first trench. The problem is that organic matter decomposes too quickly for trees to completely utilize it, thereby creating a feast-or-famine nutrient cycle. Worse, double digging mixes mulch materials into the subsoil, where they are attacked by anaerobic bacteria that excrete metabolic wastes that are actually toxic to trees and aerobic soil organisms.
The Natural Process
Trees can be kept alive in these mythical environments with a lot of attention and work. Meanwhile, the Natural Process needs little help, except in climates where it is especially hot or dry. The dry part is fairly easy to fix with irrigation. Hot depends upon how hot, but irrigation is usually the solution to hot as well.
There is an old adage: After planting, the first year a tree sleeps; the second year it creeps; the third year it leaps. It takes that long for the soil organisms to become intimately involved with the tree’s root system. If you feed the soil organisms, you can rely on nature to do the rest. So just “mulch and get out of the way!” And don’t forget that 1” – 2” of mulch is enough. The root flare should be visible after mulching.
If lush meadows and forests grow by this method, why would arborists think they can do it better?
Additional Reading
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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 Butch Ragland, edited by RW Gibney
Lush meadows and healthy forests require soil started from mulch, also known as that fresh layer of organic matter (dead grass and leaves) on the surface. Under that fresh layer of mulch is just-started compost (decaying mulch), followed by finished compost a few inches below the surface. Below all the compost comes the healthy parent soil with compost mixed throughout. This soil is ideal for healthy trees. I call this the Natural Process. In one gram of healthy soil there are as many as 3 billion organisms plus a whole range of interactions between all these organisms.
The Nitrogen-Loss Myth
Have you heard that compost uses so much soil nitrogen that you should add fertilizer to the compost pile to make it work better? The reality is that compost and mulch do not cause nitrogen to be depleted from the soil, if they are placed on top of the soil and are not incorporated into the soil by tilling. The idea that mulch causes nitrogen loss is a myth.
A host of organisms, including bacteria, worms, and fungi, break down the organic matter in mulch and compost and begin to change it into a form that will enhance tree growth by the humidification process and produce a rich soil. Research shows that this process utilizes nitrogen from air above, not the soil below.
Nitrogen is essential for making proteins in the soil. This nitrogen is stored within microorganisms' cellular structures found in the soil and in organic matter. It has been said that 75% of the nutrients in soil are stored in the microorganisms. Because of this, the nitrogen, along with many other trace minerals, cannot be leached from the soil by spring snow melt or summer irrigation. A plant’s roots will feed on the microorganism-stored nitrogen.
The Great Planting Hole Myth
University of California researchers found that putting any organic material into a planting hole caused a first-year reduction in growth of the tree planted in it. After the tree became established it recovered and grew normally. The researchers found that removing the soil from the hole, planting the tree and then putting back the removed soil around the roots gave the best results. No additional organic supplementation into the hole itself is necessary.
Arborists know that soil is a very poor container-growing medium because it is a living organism. Container-growers had to devise a method to grow trees in pots; hence a soil-less mix of sand and bark was developed. This soil-less mix is dead soil, microorganism-wise. It holds the plant upright while the growers deliver the nutrients and water that will encourage trees to grow. The techniques used to grow trees in a container do not transfer to the soil, however. This is when it makes sense to wash all the soil off the roots and plant the tree, bare root.
Grit, rock, perlite, vermiculite and all of the things used to create good drainage, moisture-holding properties, etc. and found in the container grown tree, are useless in your tree planting pit and in fact interfere with the natural process. If the soil you are planting in is surrounded by meadows or forest, it will grow trees. Since this is often impossible along city streets, rubble and poor soils such as clay and sandy soil must be changed, but the arborist cannot change them by amending the soil with magic ingredients. The poor soils must be changed by removing 75% of the existing material throughout the entire area available for the mature tree root space and mixing the remaining soil with loam and organic material such as compost to provide permeability and food for microorganisms.
Mulch makes the Soil Acidic Myth
The importance of regulating pH in the tree planting pit is another myth. Get a soil sample and send it to your local extension office or some of the larger retail nurseries, for testing. When you receive the results, base your tree selection on the test’s outcome. You cannot change the pH of your soil in any meaningful way. Soil sampling evolved out of farmers needing to control pH as they grow crops in rows. In that situation, the farmer, with the help of a tractor, has destroyed the structure of his field, and must regulate the pH and nutrient levels every year for as long as the soil is used for crops. pH adjustment is possible for turf as the root zone is in the upper 2” of soil where soil amendments are most effective.
Trees however are a different story. This is because the pH of your particular soil type will not easily move from acidic or basic toward a neutral pH, at least in the root zone, where it counts for your trees. Mulch will move your soil pH slightly toward neutral, but only at the soil/mulch interface. It is prudent to test your mulch or receive a certification of testing from the mulch producer. This should show a pH of 6.0 – 7.2 and balanced nutrient levels (NPK) in low ranges.
The Tilling Myth
How did trees grow before the rototiller? Tilling (turning the soil over but leaving it in place) and double digging are not good practices for growing trees. The double digging process requires digging a trench across the tree planting pit, then digging a second, similar-size trench next to the first, this time placing the excavated soil from the second trench mixed with organic matter into the first trench. The problem is that organic matter decomposes too quickly for trees to completely utilize it, thereby creating a feast-or-famine nutrient cycle. Worse, double digging mixes mulch materials into the subsoil, where they are attacked by anaerobic bacteria that excrete metabolic wastes that are actually toxic to trees and aerobic soil organisms.
The Natural Process
Trees can be kept alive in these mythical environments with a lot of attention and work. Meanwhile, the Natural Process needs little help, except in climates where it is especially hot or dry. The dry part is fairly easy to fix with irrigation. Hot depends upon how hot, but irrigation is usually the solution to hot as well.
There is an old adage: After planting, the first year a tree sleeps; the second year it creeps; the third year it leaps. It takes that long for the soil organisms to become intimately involved with the tree’s root system. If you feed the soil organisms, you can rely on nature to do the rest. So just “mulch and get out of the way!” And don’t forget that 1” – 2” of mulch is enough. The root flare should be visible after mulching.
If lush meadows and forests grow by this method, why would arborists think they can do it better?
Additional Reading
- Rillig, M. and Steinberg, P. D., “Glomalin production by an arbuscular mycorrhizal fungus: a mechanism of habitat modification?”, Soil Biology & Biochemistry, 34:1371-1374. 2002.
- Starbuck, Chris, “Grass Clippings, Compost and Mulch: Frequently Asked Questions”, Department of Horticulture, University of Missouri, 2003.
- Wright, S. F. and Upadhyaya, A., “Extraction of an abundant and unusual protein from soil and comparison with hyphal protein of arbuscular mycorrhizal fungi”, Soil Science, 161:575-586. 1996.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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 Diversification
By Len Phillips
A diverse palette of tree species is needed in our urban landscape to guard against the possibility of large-scale devastation by natural disasters as well as native and introduced insect pests and diseases.
History
The widespread planting of American elms in the towns and cities of eastern United States by our forefathers was a nice idea. Our early horticulturists were taking advantage of the beauty and adaptability of a native tree that Thomas Jefferson called “nature’s noblest vegetable”. The accidental introduction of Dutch elm disease, and the consequential destruction of millions of elms, served not only to focus attention on the loss of urban forests, but also to the qualities of the American elm.
Role of Diversity
We now realize that we need a diversity of tree species in our urban forests, not only to guard against disasters like Dutch elm disease, but also to “put the right tree in the right place,” as the evolution of our cities and suburbs creates challenges and new settings for tree planting.
Diversity plays an important role in the long-term stability of an ecosystem. When an area has a high diversity of tree species, it is less likely to suffer catastrophic loss from diseases or pests. For example, consider the impact the Emerald Ash Borer (EAB) has had on ash trees. The Emerald Ash Borer (Agrilus planipennis), an exotic wood-boring beetle discovered in southeast Michigan in the summer of 2002, has killed more than 10 million trees in southeast Michigan and has now spread to 36 States and 3 Canadian Provinces. Planting a diversity of hearty tree species throughout the urban forest can reduce the vulnerability of the trees to species specific pests.
Age Diversity
Consideration should be given to diversity by age within the urban forest. Planting the entire forest at one time will result in a future collapse of the entire forest at one time. A rule may also apply to age if the age of the existing forest and the number of existing trees is known. By using these two numbers one can prepare an age diversification factor for the tree replacement plan. For example: if the oldest tree in the urban forest died at 100 years of age and the tree inventory indicates a maximum capacity of 30,000 trees in the urban forest, then 300 trees should be planted every year.
Diversity by Shapes
If given enough space to grow, trees have characteristic shapes. Some shapes fit better in a space than others. Because of their vase shape, when hackberries are planted across the street from each other, their crowns form a cathedral-like arch over the street. A tree with a rounded crown will shade the yard. Pyramidal-shaped trees with dense persistent leaves provide less shade but are better at breaking the wind speed nearer the ground. A pyramidal-shaped tree also takes up more space near the ground. Trees with a weeping stature provide focal points in a landscape, as do columnar trees. Columnar trees are also suitable in locations where space is limited or a tall hedge is desired.
Diversity of Food Value
A diversity of trees with high food value is the single best way to increase wildlife populations. For example:
Keep in mind that every tree must be carefully selected for each location to be sure it is appropriate. For example, do not plant ash if the Emerald Ash Borer is on its way to your city, and sweetgums should not be planted where pedestrians are walking.
A Diversity of Wildlife Habitats
Birds and small animals need concealed spaces for nesting and hiding to protect them from the eyes of predators. Planting conifers in groups, growing hedges with low branches, or using prickly or thorny plants in a few areas are all ways to provide wildlife cover.
The Ten-Percent Rule
The “10% rule” is a reaction to the likelihood that an insect or disease pest in an urban forest with limited diversity could, at some point in time, could devastate a large portion of the urban forest. Urban foresters and municipal arborists should use the following guidelines for tree diversity within their areas of jurisdiction:
Individual trees as well as strips or blocks of uniformly planted species, cultivars, or clones with proven adaptability should be scattered throughout the city to achieve spatial as well as biological diversity.
Originally the rule was considered a safeguard against a “new pest” that might be introduced from a foreign country. The American experience with Dutch elm disease and chestnut blight is sufficient to explain the concern about such epidemics. However, the spread of dogwood anthracnose disease on our native, Cornus florida, has caused great alarm because it did not come from an introduced pathogen. There are also many “native” insect problems that we are aware of and that must be considered as potential threats to the urban forest.
“Ralph Sievert, the Director of Forestry in Minneapolis, MN Rule” developed an aggressive approach to deal with pest invasions by deciding that a phased approach to removing healthy but potentially dying trees to be replaced with young and diverse trees would mean never reaching the point where pesticide treatments were necessary. As a result, in 2014, Minneapolis adopted an 8 year-long Elm Canopy Replacement Plan (ECRP). ECRP divided removal of 5000 healthy elm trees annually with 5000 young non-elm trees. This meant convincing the public that it was necessary to preemptively remove what appeared to be healthy elm trees and replacing these trees with a diverse list of other young species, so the entire city forest retained its number of trees, but with a more diverse, healthy, and younger tree population. https://gibneyce.com/seminar-90.html#Ralph
Enacting Species Diversity
While the “10% rule” may serve as a target or goal to soothe the consciences of city councils and municipal arborists, it will not solve all potential pest problems nor guarantee the long-term stability and aesthetics of the urban forest. We need to plant more of the superior trees developed through genetic research such as found elsewhere in this Seminar. We need to utilize the practical experience from practitioners of urban forestry. We have to plan the planting of trees and understand the problems and potentials of our actions.
Enacting a species diversity plan implies three simple actions:
To achieve each of these elements, a plan containing eight tasks is necessary. The first two tasks focus on evaluating the current and potential tree resources. The remaining six tasks outline a systematic process for establishing thresholds for each species and circulating species on and off of the annual planting list.
Task 1 – Compile and assess data on the current tree population and program. An inventory is the easiest tool for collecting and summarizing this data. Necessary information includes:
Task 2 – Develop a list of all potential species to potentially plant in the area. The list should include everything from small to large and abundant to obscure. This list can be derived from several sources such as:
Task 3 – Establish a target for each species on your current list. To minimize an over emphasis of any one species on the list, a cap for each species should be established. This cap should be a percentage of the total possible number of trees that can be present in the community (existing number of trees plus the number of vacant planting sites).
Task 4 – Develop a short list of species to plant each year. This list may have anywhere from five to twenty species. This is the list of species that are going to be emphasized in the current year's planting program. The list should incorporate a variety of species in various sizes.
Task 5 – Create a threshold for each species on your annual planting list. To minimize an over emphasis of any one species on the annual list, a cap for each species should be established. As that threshold is reached, that particular species is taken off of the list for the remainder of the year. A careful balance of all suggested species for the year will guarantee an even and equitable distribution of the trees.
Task 6 – Establish a planting cycle for each species. Each species stays on the annual list for a few years. The duration is a function of how much emphasis will be placed on that particular species (the current versus the target). For example, a city might have 16 Kentucky Coffeetrees currently and a target of 266, so 250 Coffeetrees can be planted in the next few years, before this tree is removed from the tree list. Other cities have chosen to select the trees that the inventory indicates have the highest number and place a ban on using these trees until the diversification formula has been met.
Task 7 – Rotate species on and off the annual list. Once a species has reached the end of its planting cycle, it is taken off the list for a few years. Other species are then placed on the annual list to encourage their emphasis. This down time is temporary and should last anywhere from three to five years for any one species.
Task 8 – Evaluate the program. No program is complete without the ability to gauge whether or not the program is successful. The best way to assess the success or failure of a species diversity program is to compare the change over time to the individual species count and compare that count against the targets you have established for each species. Continue to assess the suitability of species and incorporate changes due to insect/disease, cultural, or other realizations.
Benefits of Diversification
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.
By Len Phillips
A diverse palette of tree species is needed in our urban landscape to guard against the possibility of large-scale devastation by natural disasters as well as native and introduced insect pests and diseases.
History
The widespread planting of American elms in the towns and cities of eastern United States by our forefathers was a nice idea. Our early horticulturists were taking advantage of the beauty and adaptability of a native tree that Thomas Jefferson called “nature’s noblest vegetable”. The accidental introduction of Dutch elm disease, and the consequential destruction of millions of elms, served not only to focus attention on the loss of urban forests, but also to the qualities of the American elm.
Role of Diversity
We now realize that we need a diversity of tree species in our urban forests, not only to guard against disasters like Dutch elm disease, but also to “put the right tree in the right place,” as the evolution of our cities and suburbs creates challenges and new settings for tree planting.
Diversity plays an important role in the long-term stability of an ecosystem. When an area has a high diversity of tree species, it is less likely to suffer catastrophic loss from diseases or pests. For example, consider the impact the Emerald Ash Borer (EAB) has had on ash trees. The Emerald Ash Borer (Agrilus planipennis), an exotic wood-boring beetle discovered in southeast Michigan in the summer of 2002, has killed more than 10 million trees in southeast Michigan and has now spread to 36 States and 3 Canadian Provinces. Planting a diversity of hearty tree species throughout the urban forest can reduce the vulnerability of the trees to species specific pests.
Age Diversity
Consideration should be given to diversity by age within the urban forest. Planting the entire forest at one time will result in a future collapse of the entire forest at one time. A rule may also apply to age if the age of the existing forest and the number of existing trees is known. By using these two numbers one can prepare an age diversification factor for the tree replacement plan. For example: if the oldest tree in the urban forest died at 100 years of age and the tree inventory indicates a maximum capacity of 30,000 trees in the urban forest, then 300 trees should be planted every year.
Diversity by Shapes
If given enough space to grow, trees have characteristic shapes. Some shapes fit better in a space than others. Because of their vase shape, when hackberries are planted across the street from each other, their crowns form a cathedral-like arch over the street. A tree with a rounded crown will shade the yard. Pyramidal-shaped trees with dense persistent leaves provide less shade but are better at breaking the wind speed nearer the ground. A pyramidal-shaped tree also takes up more space near the ground. Trees with a weeping stature provide focal points in a landscape, as do columnar trees. Columnar trees are also suitable in locations where space is limited or a tall hedge is desired.
Diversity of Food Value
A diversity of trees with high food value is the single best way to increase wildlife populations. For example:
- Summer Fruit – cherries, dogwoods, plums, apricots
- Fall and Winter Fruit – apples, crabapples, dogwoods, hackberries, hawthorns, mountain ashes
- Seeds – ashes, birches, firs, hemlocks, maples, spruces, sweetgums
- Nuts and Acorns – butternuts, walnuts, chestnuts, hazelnuts, hickories, oaks, pecans
Keep in mind that every tree must be carefully selected for each location to be sure it is appropriate. For example, do not plant ash if the Emerald Ash Borer is on its way to your city, and sweetgums should not be planted where pedestrians are walking.
A Diversity of Wildlife Habitats
Birds and small animals need concealed spaces for nesting and hiding to protect them from the eyes of predators. Planting conifers in groups, growing hedges with low branches, or using prickly or thorny plants in a few areas are all ways to provide wildlife cover.
The Ten-Percent Rule
The “10% rule” is a reaction to the likelihood that an insect or disease pest in an urban forest with limited diversity could, at some point in time, could devastate a large portion of the urban forest. Urban foresters and municipal arborists should use the following guidelines for tree diversity within their areas of jurisdiction:
- plant no more than 10% of any species,
- no more than 20% of any genus,
- no more than 30% of any family.
Individual trees as well as strips or blocks of uniformly planted species, cultivars, or clones with proven adaptability should be scattered throughout the city to achieve spatial as well as biological diversity.
Originally the rule was considered a safeguard against a “new pest” that might be introduced from a foreign country. The American experience with Dutch elm disease and chestnut blight is sufficient to explain the concern about such epidemics. However, the spread of dogwood anthracnose disease on our native, Cornus florida, has caused great alarm because it did not come from an introduced pathogen. There are also many “native” insect problems that we are aware of and that must be considered as potential threats to the urban forest.
“Ralph Sievert, the Director of Forestry in Minneapolis, MN Rule” developed an aggressive approach to deal with pest invasions by deciding that a phased approach to removing healthy but potentially dying trees to be replaced with young and diverse trees would mean never reaching the point where pesticide treatments were necessary. As a result, in 2014, Minneapolis adopted an 8 year-long Elm Canopy Replacement Plan (ECRP). ECRP divided removal of 5000 healthy elm trees annually with 5000 young non-elm trees. This meant convincing the public that it was necessary to preemptively remove what appeared to be healthy elm trees and replacing these trees with a diverse list of other young species, so the entire city forest retained its number of trees, but with a more diverse, healthy, and younger tree population. https://gibneyce.com/seminar-90.html#Ralph
Enacting Species Diversity
While the “10% rule” may serve as a target or goal to soothe the consciences of city councils and municipal arborists, it will not solve all potential pest problems nor guarantee the long-term stability and aesthetics of the urban forest. We need to plant more of the superior trees developed through genetic research such as found elsewhere in this Seminar. We need to utilize the practical experience from practitioners of urban forestry. We have to plan the planting of trees and understand the problems and potentials of our actions.
Enacting a species diversity plan implies three simple actions:
- Minimize planting overused species.
- Increase the planting of underused species.
- Introduce new species into the landscape.
To achieve each of these elements, a plan containing eight tasks is necessary. The first two tasks focus on evaluating the current and potential tree resources. The remaining six tasks outline a systematic process for establishing thresholds for each species and circulating species on and off of the annual planting list.
Task 1 – Compile and assess data on the current tree population and program. An inventory is the easiest tool for collecting and summarizing this data. Necessary information includes:
- Species count and percent representation in the population.
- Number of vacant planting sites in the community.
- Number of trees planted each year.
- Number of trees removed each year.
- Contents of the annual planting list.
Task 2 – Develop a list of all potential species to potentially plant in the area. The list should include everything from small to large and abundant to obscure. This list can be derived from several sources such as:
- the current tree population highlighting all the species that currently appear to be doing well,
- planting lists from neighboring communities,
- local arboreta or botanical garden lists,
- tree, shrub, and landscape books,
- trees selected from the list in this and previous Seminars.
- nursery catalogs that match zone restrictions for your area.
Task 3 – Establish a target for each species on your current list. To minimize an over emphasis of any one species on the list, a cap for each species should be established. This cap should be a percentage of the total possible number of trees that can be present in the community (existing number of trees plus the number of vacant planting sites).
Task 4 – Develop a short list of species to plant each year. This list may have anywhere from five to twenty species. This is the list of species that are going to be emphasized in the current year's planting program. The list should incorporate a variety of species in various sizes.
Task 5 – Create a threshold for each species on your annual planting list. To minimize an over emphasis of any one species on the annual list, a cap for each species should be established. As that threshold is reached, that particular species is taken off of the list for the remainder of the year. A careful balance of all suggested species for the year will guarantee an even and equitable distribution of the trees.
Task 6 – Establish a planting cycle for each species. Each species stays on the annual list for a few years. The duration is a function of how much emphasis will be placed on that particular species (the current versus the target). For example, a city might have 16 Kentucky Coffeetrees currently and a target of 266, so 250 Coffeetrees can be planted in the next few years, before this tree is removed from the tree list. Other cities have chosen to select the trees that the inventory indicates have the highest number and place a ban on using these trees until the diversification formula has been met.
Task 7 – Rotate species on and off the annual list. Once a species has reached the end of its planting cycle, it is taken off the list for a few years. Other species are then placed on the annual list to encourage their emphasis. This down time is temporary and should last anywhere from three to five years for any one species.
Task 8 – Evaluate the program. No program is complete without the ability to gauge whether or not the program is successful. The best way to assess the success or failure of a species diversity program is to compare the change over time to the individual species count and compare that count against the targets you have established for each species. Continue to assess the suitability of species and incorporate changes due to insect/disease, cultural, or other realizations.
Benefits of Diversification
- Diversification will mean making better use of the tree species commonly planted in your city, while ensuring that they are well suited to the site in the context of predicted climate change.
- Take opportunities to use tree species not historically widespread in your city, but which will become more suitable under current climate change predictions.
- Be sure that you have given consideration to a choice of silvicultural systems when making decisions on species and mixtures.
- Make sure that any group mixtures are of compatible species, and they will meet the long-term management objectives.
- Use existing or expected natural regeneration to diversify stands where the species you expect will be able to meet the set objectives and will remain well suited to the site, even where you are not practicing diversification.
- When thinning or re-spacing, take the opportunity to retain minor species where they will contribute to the long-term objectives of the urban forest.
Sources
- ”A guide for increasing tree species diversity in Wales” Forestry Commission on Wales, November 15, 2010.
- Duntemann, Mark, “Urban Forestry Management Series: Implementing a Species Diversity Program”, Natural Path Urban Forestry Consultants, July, 2004.
- Santamour, Frank S., Jr., “Uniformity and Common Sense”, METRIA 7 Proceedings, 1990.
- National Arbor Day Foundation, “Tree Diversity Activity”, 2009.
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, Municipal Specialist, Tree Worker/Climber, Utility Worker, Tree Worker/Aerial Lift, or 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.