ARCHIVE #66

Seminar #66 from Online Seminars for Municipal Arborists – January / February 2016

Sections Go directly to the section by clicking on the titles below.

*** A Better Way to Grow City Trees ***
Recommending Street Trees
Tree of the Seminar 66 - Red November Maple
Moving Palms
Right Tree - Right Place
Marcescence
Cultivars of Silverbell
Complete Streets Movement

Note: Click on green text in each section for more information.

                                             *** A Better Way to Grow City Trees ***
                                                                            Edited by Len Phillips

Is there a better way to promote tree root growth in the soil under a city sidewalk and reduce the infrastructure conflicts? Yes. A study was started last year by Dr. Tom Smiley at the Bartlett Research Laboratory to compare the effect of various subsurface treatments on tree growth. These treatments included Amsterdam-like soil, two soil cell products, a type of Cornell's CU-Structural Soil and two control plots.

Some Chinese tulip trees Liriodendron chinense were planted in six 90 feet (30 m) long plots that duplicated city conditions. The soil is 2 feet (60 cm) deep, and 5 feet (1.5 m) wide. The trench was lined with Typar fabric to restrict roots from growing outside of the trench. At five foot intervals, wood barriers were constructed to hold the fabric and separate each of the plots so each plot contained only 42 cubic feet (1.2 cm) of soil, similar to what might be expected in a city sidewalk. The six plots were duplicated to provide replication and the growth rates are an average of the 6 plots.

Treatments
The different treatments were:
1.    Control – the soil mix was compacted to 80% Proctor and there was no concrete over the soil.
2.    Compacted control – same as the above but the soil mix was compacted to 95% Proctor to meet current standards for compaction under streets and structures – typically found in most cities.
3.    Silva Cells – the soil mix was compacted to 80% Proctor within the Silva Cell structure.
4.    StrataCells – the soil mix was installed within the cells at the direction of the manufacturer but the soil density was not tested.
5.    Sand Based Structural Soil (SBSS) – the soil mix was very similar to Amsterdam soil. The basic formula was 4 parts medium to coarse (concrete) sand, 1 part topsoil loam and 1.5 parts mature compost. It was compacted to 94 – 96% Proctor.
6.    CU Structural Soil – a gravel based mix was defined and compacted according to specifications of Cornell University publications. The basic mix was 80% #5 stone, 20% soil mix and 0.003% hydrogel. The mix was compacted to 95% Proctor.

The plots were filled, compacted as noted above, and planted in July 2014. After the trees were planted, a two inch (5 cm) layer of concrete was poured over all the plots to replicate a sidewalk, and a nine inch (22 cm) diameter hole was left in the middle of the plot to accommodate the tree's trunk growth and irrigation.

One year later, in September 2015, the tree growth data was collected and the tree height, diameter, condition, dieback, and leaf color were all measured. Leaf moisture and chlorophyll fluorescence were also determined. The first year's growth has indicated a startling result as indicated in the abbreviated list below.

Results
The results were calculated by measurement of each of the six soil treatments and the 6 plots were averaged.
1.    Control                             51 cm (22 inches) height increase, 18 cm (7 inches) spread
2.    Compacted control             9 cm ( 3 inches) height increase,   8 cm (3 inches) spread
3.    Silva Cells                         85 cm (34 inches) height increase, 29 cm (30 inches) spread
4.    StrataCells                       88 cm (36 inches) height increase, 25 cm (25 inches) spread
5.    SBSS                                42 cm (17 inches) height increase, 18 cm (7 inches) spread
6.    CU Structural Soil             33 cm (13 inches) height increase, 12 cm (5 inches) spread

The height of growth for the 2015 growing season and total spread numbers clearly illustrate that soil cells out-performed all the other methods.

Soil Cells
The soil cells studied in this research allow for support of the infrastructure above, while providing a large less compacted soil volume within the cell structure. Two soil cell products available in the U.S. and Canada are:

Silva Cells are a type of soil cell that look like industrial shelving and can be staked to various heights before they are topped with a deck. Each stack of Silva Cells is completely open along both vertical and horizontal faces and the stacks stand independently, making future excavation and repairs simple and avoid any impact to the rest of the system. They can be spread laterally as wide as necessary. They are plastic units manufactured by Deep Root.
StrataCells, manufactured by GreenBlue, are made from 100% recycled plastic that can be stacked to various heights and cut and shaped as required during construction. They are one component modules that clip together to form a skeletal matrix which is then filled with soil This makes for a quick and easy installation compared to multiple component systems. They can also be spread laterally as wide as necessary including under vehicular traffic areas with minimal surface coverage.

Both products are placed on a compacted surface at the bottom of the enlarged planting vault. The weight of the pavement and any surface loading is transferred downward by the cells to the compacted surface at the bottom of the planting vault while the soil within the cells remains loose and more suitable for a tree's root growth. The optimum amount of high quality soil for tree root growth also provides a stormwater reservoir function. Excess water infiltration into the vault is escapes through a drain at the bottom of the vault.

Each soil cell supports the hardscape and can meet AASHTO H-20 loading requirements with proper engineered surfaces above, as reviewed by a qualified engineer.   Irrigation and aeration systems as well as local utilities can be integrated into the soil cell layout. Water can also enter the system through pervious paving, drains, catch basins, and the opening around the tree trunk.

In 2011, Online Seminars conducted an effort to objectively compare soil cells and structural soil. Both of these planting techniques are more expensive than conventional urban street tree planting sites in existing soil. However, the research demonstrated they are both much better in terms of supporting long-term tree growth. While they are not practical for infrastructure replacement projects around existing trees, they should be considered for every new sidewalk and street tree construction project that is has the space for creating 100 square feet (9.3 square meters) of soil space or more, and can potentially connect tree planting sites with linear increased soil volumes. Of the soil cell products in the Bartlett test, trees growing in Silva Cells demonstrated the most branch spread after one year, while the trees growing in StrataCells demonstrated the most height change in the first year. However, there was no significant difference between the two products.

The factors that most designs and research experiments do not consider are the mature size of the tree’s flare and root crown expansion. If the final soil grade is left below the bottom of the deck by the anticipated root crown expansion, and the sidewalk opening for the tree is designed to exceed the mature trunk size, the conflicts with the infrastructure should be greatly reduced over the life of the tree.

Conclusion
The use of soil cells should provide more soil volume, more available soil space, and improved tree growth. The research also supports that less compaction improves tree growth.

If you are interested In sending out a bid to purchase and install soil cells, here is a Specification you might want to use.

Endorsements
The value of this research has been expressed by some leading supporters of soil cells.

“This research further confirms that trees grow best in (1) loamy soils with intact structure, and (2) in rooting areas that are open both vertically and horizontally. We know that tree-friendly urban design is possible, yet we still struggle to get designers, owners, and builders to change their approach. We hope Dr. Smiley’s research will continue to push Urban Forestry in the direction of providing city trees with what they need to grow, mature, and provide meaningful environmental services.”
                                                                                               Leda Marritz, Creative Director at Deep Root

“Dr. Smiley's work is a significant step in understanding the relationships of trees, soils, and pavements. Other areas of design that are equally important to successful trees that arborists and designers need to understand include, providing the right spacing between trees for a reasonable canopy growth; harvesting rain water into the root zone under the pavement; and assuring that trees are purchased with proper root systems. Good arborists can work with the tree's natural functions and still make beautiful places that respect trees.”
                                                                            Jim Urban, Landscape Architect, Author of “Up by Roots"

“The research conducted by Dr. Smiley is great evidence that trees planted in hardscape areas with structural
systems to provide un-compacted soil zones, drastically improves urban planting success, while providing the
benefits to our areas of urban infrastructure that only a tree can provide. The research evidence clearly proves that trees are assets in our cities and should not only be protected, but also provided for, to allow for the long- term sustainability that we are now understanding is critical to the built environment which includes the management of storm-water solutions at the source.”
                                                                    Jeremy Bailey, Consultant at GreenBlue Infrastructure Solutions

“If the site is right and compaction is not an issue, we can get by without soil cells. Once the site is compacted, if we want trees to grow in deep soil, we need to consider some activity such as soil remediation or the installation of soil cells.”                                         Gordon Mann, Consulting Arborist and Urban Forester

Sources

Discussions with the endorsers and Shane Carpani with GreenBlue.
Smiley, E. Thomas Ph.D., “Comparison of Methods of Soil Management Under Pavement”, Bartlett Tree Research Laboratories, 6/4/2014
Phillips, Len, “Two Ways to Successful Planting“, Online Seminars Topic #5, 2011.

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 .5 CEUs toward Certified Arborist, Municipal Specialist, Tree Worker Specialist 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 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.

                                                      Recommending Street Trees
                                                                                 By Len Phillips

What is an ideal street tree?
It should tolerate the local urban environment and pollution problems.
It should live at for least 50 and preferably 100 years.
It should be beautiful all year round.
It should have few pest problems.
It should be disease resistant.
It should tolerate local soils.
It should be hardy.
It should tolerate road salt.
It should have seasonal color.
It should not be dropping fruit.
It should need little maintenance.
It should not be susceptible to die back.
It should not have brittle limbs or anchorage problems.
It should not have surface roots, especially for growing near sidewalks.

However, since one perfect street tree does not exist, tree selections should be made by using the best trees that we do have. The first step consists of creating a list of trees that are currently doing well in your city. The list can be composted of the tried and true from previous planting experience and the results of the best trees found in the street tree inventory. This list is modified by removing those materials that experience has indicated do poorly in local roadside or urban conditions. Also remove from this list, trees with high maintenance costs, surface roots, intolerance to storms, and undesirable fruiting habits.

Then add natives, cultivars of natives, and hardy trees that are likely to tolerate the local conditions. Add trees that are tough in terms of pest resistance and those that should do well in the city. It is advisable to compare the selections with what other authorities and neighboring cities have recommended. Also review books, local universities, and extension services. Local nurseries can be used in order to determine what species are available as well as those that the nursery has recommended. The internet might be helpful for providing information about specific trees provided the source is fairly local such as this University of Florida website.

Once a list of trees is compiled, it should remain open so new trees can be added and failures can be deleted as the situation warrants.   The list of trees to be used should cover half the trees being ordered for the next planting season. The other half of the order should include 2 – 10 trees each of species or cultivars of trees that might be suitable but are untried in your community. These trees should be considered as a trial to see how well they tolerate your city. Those that look great can be added to the recommended list of trees and the trees that do poorly can be added to a list of trees that should not be used again. The reason for selected 2 – 10 trees is to reduce the expense if the trees are a failure and have to be replaced. Two trees would be suitable on a limited budget and you are planting 300 trees or less. Ten trees would be suitable for the largest cities where the trees could be planted in different locations all around the city to see if one spot might be better than others.

Once the tree planting list is established it can be used to fit the trees to the planting sites in accordance with the municipal regulations, utilities, structures, climate, arboricultural standards, and other urban and environmental factors. The size of the tree at maturity must also be considered when locating a tree at its permanent site. The planting list should be made a part of the Street Tree Master Plan.

Unacceptable Trees
There may be species that are known to be unacceptable in your region or have failed in your city. These should be posted on a list of unacceptable trees and made a part of your Street Tree Master Plan so future removal expense is postponed. Any failures from your trials should also be added to this list. By keeping track of the failures, new cultivars might come along that will tolerate the reason for failure. Since you know what the problem is, you should try the new tree to see if it is successful in avoiding the problem.

Diversification Formula
The Diversification Formula has been developed to prevent an over dependence on a single genus such as ash or American elm. The Diversification Formula was established by the International Society of
Arboriculture (ISA) and is now an accepted standard throughout the United States and other countries around the globe. The Formula is defined as a planting plan containing:

no more than 10% of any species,
no more than 20% of any genus,
no more than 30% of any family.

Enacting a species diversity plan implies three simple actions:

minimize planting of overused species,
increase the planting of underused species,
introduce new species and cultivars into the landscape.

The Diversification Formula should be carried one step further. It should be applied to the existing street tree inventory so the dependence on a single species from previous or natural plantings will not be carried forward into future planting. The Diversification Formula was set up so if, for example 3% of a city’s tree population contained red oak and a disease or insect killed them all, then 97% of the trees would still remain. The American elm was as much as 50% of the urban tree population before Dutch elm disease devastated landscapes across North America. The Emerald Ash borer is repeating the process and going for the ash trees that many communities planted to replace the American elms. The Diversification Formula may be difficult to use in places where the number of trees is severely restricted due to soil or climatic conditions, but that does not mean that diversification can be ignored.

The City of Lansing, Michigan has a diversification policy which states: “No Tree will be planted next to a tree of the same species and at least four genus will be planted on every street block.” This adaptation of a diversification policy works very well. The result is that Lansing still has tree-lined streets despite the fact that the Emerald Ash borer has been in the area since 2002 and most cities in the region have lost almost all of their trees.

Aesthetic Value
Aesthetics and function should work together to determine the selection of an urban tree species. What is the purpose of the tree? Is it to screen views, provide shade, enhance the aesthetics, enclose a space or improve the site and environment? Definite shaped trees and ornamental flowering or fruiting trees should be carefully selected and located to avoid distractions to a driver while at the same time used to improve aesthetics. The tree itself can become the focal point through unique color, spectacular flowers, large fruit, or fall foliage. Trees should be used to assist in defining the edge of the roadway and enhancing spatial qualities. Spacing between trees should vary from 30 to 150 feet apart to create a naturalized appearance, and if one tree dies or is removed it does not spoil the continuity of the planting.

Trees need sufficient unpaved areas and good soil for maximum health and vigor. They should be allowed to develop into perfect specimens and true representatives of their species. They should not be dangerously close to traffic in the street and could, if local ordinances allow, be planted behind the sidewalk to take advantage of good soil, open space, and a better growing environment.

Blocks versus Mixed Design
Street tree plantings can be designed in one of two layouts depending upon the city, past practice, and location in the US. Block planting means that an entire block of a city street will have only one species of tree planted on that block. Ideally the trees are all planted at the same time so they look the same throughout their lifetime. Aesthetically, all trees look identical on the block, which unifies a neighborhood with a common species.   The space can be equal and in the mid-western and western states, this planting concept is quite compatible with the grid of the street patterns. This design provides a feeling of unity, equality, and aesthetic compatibility. This makes the maintenance requirements considerably less because all maintenance would be approximately the same on each tree. Theoretically, the Diversification Formula is not violated since the next block would contain a totally different species. However, this planting style can mean planting trees in inappropriate locations and a disease or pest will wipe out the whole block at once.

Mixed plantings mean diversity because each tree on a city block is different than the tree beside it. The trees can be planted with different spacing, sizes, and shapes. Many cities prefer this design approach since each house is different; the tree can also be different. This design is customarily found where the streets flow in random or curvilinear patterns. This planting concept also tends to keep the trees healthier because diseases will not progress from one tree to the next and trees grow naturally in random sizes, spacing, and species. However, maintenance costs will be higher and there may not be the aesthetic harmony that would be apparent with block planting. Many people prefer this concept because it seems more natural and sustainable.

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 .5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker Specialist, Aerial Lift Specialist, 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 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 of the Seminar 66 - Red November™ Amur Maple
                                                                            By Len Phillips

Red November™ Maple features bright green foliage that stays fresh and clean despite summer stress. The small size of this Amur Maple cultivar makes it an ideal tree for planting between the street and the sidewalk.

Trade Name:             Red November™ Amur Maple                                                                                        Botanical Name:       Acer ginnala ‘JFS-UGA’                                                                                         Parentage:                 Selected by Dr. Michael Dirr,
Family:                       Aceraceae
Introduction: J. Frank Schmidt & Son nursery introduction in 2010
Hardiness Zone:       4 – 10
Height:                      15' – 20'
Spread:                     20' – 25'
Growth Rate:            Slow, 20' in 20 years
Form:                         Low branched or multi-stemmed tree creating a round form
Bloom Period:           Late April to early May
Flower:                       Fragrant, showy, yellowish white
Fruit:                          Bright red seeds are thin and winged samaras
Summer Foliage: Bright green, fine textured
Autumn Foliage:    Bright red fall color develops later than that of typical A. ginnala seedlings
Winter Interest:    Handsome and refined bark provides winter interest
Bark:                          Brown and slightly shaggy
Habitat:                      Grows throughout the eastern half of the U.S.
Culture:                      Prefers moist, well drained soil, Red November will tolerate summer heat
Pest Problems:          None serious, good resistance
Storm Resistance:    Good
Salt Tolerance:          Good
Planting:                   Easy to transplant bare root
Propagating:     Softwood cuttings
Design Uses:     Shade tolerant specimen for lawns, parks, and street trees under utility wires
Companions:     Use with evergreen groundcovers
Other Comments:      This heat adapted Amur maple evolved from the heat of Georgia should perform well all                                      across the South
Photo:                        J. Frank Schmidt & Son

Sources
This information has been gathered from personal observations of the author, living in Massachusetts, Zone 6, and information provided by J. Frank Schmidt & Son nursery.

The test that follows contains 10 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.

ISA will award .5 CEUs* for a passing grade. SAF members will earn 0.5 Cat. 1-CF for every five passing test scores. The cost for taking this test is $10. If you purchase an annual subscription for 15 credits, the cost per credit is reduced by 50% (see Annual Subscription link below). We will report all passing test scores to ISA and/or SAF. If you are a member of ISA and SAF we will report your passing test scores to both for no additional cost. Please be sure to add both of your certification numbers when you sign in. Tests with passing scores may be submitted only once to each organization.

*Members of ISA may apply the .5 CEUs toward Certified Arborist, Municipal Specialist, Tree Worker Specialist, Aerial Lift Specialist, 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 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.

                                                                  Moving Palms
                                                                            Edited by Len Phillips

Palms are not trees. They do not have a cambium and are not capable of generating new tissue to cover injured areas. Due to their tender qualities, when moving palms, efforts must be made to avoid any mechanical damage to their trunks. Terminal buds of palms must be carefully protected from damage, since it is only from this structure that new growth develops. Palms are considered a tropical plant growing in warm climates.

Digging
Palms are often moved with very small root balls. When the sandy soils are allowed to fall off the roots that do remain, the method might be better described as bare root. Bare root palms must be treated the same way that a bare root tree is handled. Keep the roots moist at all times and syringe the leaves with water when they show signs of wilt.

For cabbage palms (Sabal palmetto) and other species that regenerate all of their new roots from the base of the trunk instead of the severed root ends, bare root transplanting may be acceptable. Other palms would benefit from more typical root ball or B&B procedures. Large multi-stemmed palms may require a ball of 10 to 12 ft diameter. In California and Arizona, transplanting palms is more successful during April to September when the soils are warmer and root development is more readily stimulated.

Storage
Palms not immediately replanted should be heeled-in like any other plant. Transferring palms to containers is another good way to store these plants. Irrigation and protection from intense sun are important when palms are waiting to be planted. Palms awaiting planting should also be staked in an upright position while in storage to prevent damage to the terminal bud.

Transporting
Some or all of the palm leaves are often removed prior to transport, rather than waiting to prune them at the planting site. However, this practice is being investigated to determine if it is really necessary. The proper method varies with species and circumstances. Palms are lifted in most instances by means of a strap or sling placed just above the estimated center of gravity on the trunk. The small size and weight of the root ball offers no logical means of lifting by the ball. Nylon slings should be used because they offer a high degree of protection for the palm trunk. When a sling is being attached to the trunk, the surface must be protected from burn or compression marks that will form permanent scars.

When many single-stemmed palms are to be transported, they can be laid flat or shingled on a flatbed trailer. Transplanted palms with long slender trunks should have a supporting timber attached to its trunk during transport. The tops should always be tied securely. This important protective support is justified because the alternative is the possible loss of the essential terminal bud and the ultimate death of the palm.

Root Development
Palm roots emerge from the trunk at the root initiation zone. This zone can develop a swelling at the base of the trunk. Palms that are planted too deeply have no swelling at the base and should be replanted higher.

It is commonly believed that if the tube-like roots of palms are cut during the digging process they will usually die back and new roots will originate from the root initiation zone at the base of the trunk. Actually, regrowth response of cut palm roots varies with species and distance from the base of the trunk.   Less than 1 percent of all cut cabbage palm (Sabal palmetto) roots regenerate root tips, whereas coconut palms (Cocos nucifera) regenerated root tips about 50 percent of the time regardless of root stub length. Queen (Syagrus romanzoffianum) and royal palms (Roystonea sp.) regenerated new roots at the tips of the cut root. The number of new roots became greater as the length of the root stub increased. Root pruning stimulated new roots from the root initiation zone for all species, but at a rate inversely proportional to the ability of the species to regenerate root tips on severed roots.

Pruning
In the past, the common practice was to remove 2/3 or more of palms leaves before transplanting. Recent research has reversed this practice and indicated that with regular irrigation, palm quality and root growth increased as the number of leaves retained was increased. However, in drought, the reverse is true. The practice of tying the leaves into a bundle to protect the bud from drying has been found to have no positive effect and could actually lead to fungal infection in the bud if irrigation or rainfall were frequent.

The current recommendation for species where no specific research data is available is to remove no more than 1/3 of the leaves if the plant is moved with a small root ball. It is not necessary to remove any leaves of palms grown in containers or moved with a tree spade. If irrigation is ample, the leaves do not need to be removed on any palm regardless of the transplant method. If leaves are pruned off before moving, the palm does not need to have additional leaves removed at the planting site.

Sources

Gilman, Edward F., "Planting trees in landscapes", Environmental Horticulture Department, IFAS, University of Florida, 2004.
Watson, Gary W. and E. B. Himelick, "Principals and Practice of Planting Trees and Shrubs"', International Society of Arboriculture, Savoy, IL 1997.

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 .5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker Specialist, Aerial Lift Specialist, 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 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.

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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.

                                                            Right Tree – Right Place
                                                                                   By Len Phillips

Planting sites can be a major challenge to the arborist working in an urban environment. We have all heard that the answer to this is simply growing the right tree in the right location for the right reasons. But what does this really mean? Most arborists have an idea of what it means to them. Here are my opinions on this subject.

Growing the Right Tree
First of all, the right tree is a tree that will do well with the urban atmosphere; it will tolerate urban soils; and it will grow despite all the abuse and lack of care that one finds on trees in our cities. The mature tree size is an important factor in selecting the right tree. One reason is not planting a large shade tree under the utility wires or in a small space. While this should be obvious, I recall on a couple occasions working with residents about where to plant their tree, I looked for indicators of all the underground utilities, shade and root competition from other trees, lawn sprinklers, property lines, tree qualities desired by the resident, etc. but I forgot to look up. It was then I saw wires directly overhead.

The right tree should also be resistant to serious insect and disease problems. Will it grow with a minimal amount of care? Is the form and aesthetic value of the tree suitable for the site? Does the tree possess the attributes you want for the site and are its liabilities too much for the care the tree is expected to receive? Are there sufficient maintenance funds available to care for the tree?

Selecting the Right Place
Is the site able to provide for the space and needs of the tree? It is very difficult to try to squeeze a large shade tree into that three foot (90+ cm) wide ribbon of green between the sidewalk and the street. If you restrict the root space, you will restrict the crown development, possibly the tree health, and shorten the tree longevity. As someone else said, “When the good soil for root space is full, growth stops, and decline begins.” If you do not have adequate root space you will have to plant a smaller tree or expand the root space by improving the planting soil deeper and wider, improving the soil deep under the sidewalk, or by using structural soil or soil cells under the street and sidewalk to provide the necessary amount of soil and pore spaces for roots, oxygen, and water.

If none of the above options will work, call the green ribbon a utility strip and don’t plant anything in it. Using this option, all new trees are planted behind a relocated sidewalk, or on private property where there is more room for the roots and crown to spread. I have used this approach for many years and discovered that the trees grow faster and achieve a nice canopy over the street in a shorter period of time compared to the same tree planted next to the street where it has to deal with road salt, exhaust fumes, compaction, damage from vehicles, etc.

The soil conditions at the site should be suitable to support the long-term growth of the tree. Consider the soil's fertility level and pH. Check the soil type, the amount of soil, and porosity to be sure it is suitable for the tree being selected.

Planting sites should be large enough to accommodate the tree's roots at maturity. Published research reports indicate five square feet (4.5 sq. meters) of soil surface area for every one square inch (6.5 sq cm) of trunk diameter the tree is expected to attain, or two cubic feet (0.06 cm) of soil for every square foot (0.1 sm) of the future crown projection (which is the area under the drip line). The soil should always be about three feet (90 cm) deep for normal growth and vigor. A simpler method consists of the following:

trees larger than 50 ft tall or spread need 2,700 cu. ft. of soil,
trees that grow 30 to 50 ft tall or spread need 1,200 cu. ft. of soil,
trees that grow less than 30 ft tall need 600 cu. ft. of soil,

Right Tree Guide
I would like to offer a guide for what trees should be planted within a given area for proper root development. The guide of species and cultivars below are trees that tolerate the urban environment based on my experience in the Boston, Massachusetts area as well as the recommendations from leading arborists around the US that I have talked with.

This guide has been developed to do the calculations for you. Listed below are excellent street trees, their height, spread, and trunk diameter at maturity, and the amount of surface area in square feet for a planting site three feet (1 m) deep. An asterisk (*) denotes trees that are extremely tough and will tolerate most urban soils. All other trees will do well in suburban soil locations and urban sites with improved soil. This list is a guide and must be adapted to your locality.

The size indicated is the maximum growth that the particular tree could attain with an ideal root space. The sizes of the trees indicated come from nurseries where the soil conditions are close to perfect. You may have to modify these numbers for your local climate and the site. Irrigation will alter the root area requirements, as will the local rainfall.

Not indicated on this list are the qualities of each tree. What colors does the tree have in each of the seasons; what soil pH will it tolerate; what are the leaf characteristics and branching structure; is the tree disease and pest resistant; are fruits and dropping branches an issue; how fast will it grow; and what means of transplanting works best. The links on each tree will help provide some of this information. One other excellent means of assisting you with the selection process is this University of Florida website. This site was developed in cooperation with the USDA Forest Service. The site develops a list of trees according to your soil, desired tree size, plant attributes, site requirements, etc. Click on various items and a list appears for you. This is a great resource that should be listed on your computer’s favorites/bookmark list.

Don’t forget to consider the function of each tree in the landscape. Is it there to provide shade, block a view, provide a street canopy, etc.? On the other hand, will the tree block the view of a store or will the dropping leaves or fruit be a problem to neighboring urban uses. These are all features about each of the trees on your plant list that you should know, if you are truly trying to grow the right tree in the right place.

Species                                             Trade                                       Height (ft)     Crown    Diameter Area (sf) Surface                                              Name                                                           Spread Trunk (in)
-------------------------------------------------------------------------------------------------------------------------------------------------
Acer campestre Hedge Maple * 30 30 12 16
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer x freemanii Autumn Blaze Maple * 50 40 24 32
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer x freemanii   Celebration Maple * 45 20 24 32
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer x freemanii Marmo Maple * 55 45 24 32
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer glabrum Rocky Mountain Maple 25 15 6 8
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer miyabei State Street Maple * 50 35 24 32
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer nigrum Green Column Maple 50 20 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer platanoides Deborah Maple * 45 40 36 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer rubrum Armstrong Maple * 45 15 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer rubrum Autumn Flame * 35 35 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer rubrum Bowhall Maple * 40 15 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer rubrum Karpick Maple * 40 20 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer rubrum October Glory Maple 40 35 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer rubrum Red Sunset Maple * 45 35 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer rubrum Sun Valley Maple 40 35 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer saccharum Apollo Maple 25 10 20             27 --------------------------------------------------------------------------------------------------------------------------------------------------
Acer saccharum Bonfire Maple 50 40 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer saccharum Commemoration Maple 50 35 30            40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer saccharum Endowment Maple 50 20 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer saccharum Green Mountain Maple 45 35 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer saccharum Legacy 50 35 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer saccharum Steeple Maple 45 20 30           40 --------------------------------------------------------------------------------------------------------------------------------------------------
Acer tataricum Rugged Charm Tatarian Maple * 25 20 12 16
--------------------------------------------------------------------------------------------------------------------------------------------------
Acer truncatum Norwegian Sunset Maple * 35 25 30 40
--------------------------------------------------------------------------------------------------------------------------------------------------
Aesculus x carnea Fort McNair Horsechestnut 70 30 48 64
--------------------------------------------------------------------------------------------------------------------------------------------------
Amelanchier laevis Snowcloud Serviceberry 25 15 5 10
--------------------------------------------------------------------------------------------------------------------------------------------------
Betula nigra Dura-Heat Birch * 40 30 28 37
---------------------------------------------------------------------------------------------------------------------------------------------------
Betula nigra Heritage Birch * 40 30 28 37
---------------------------------------------------------------------------------------------------------------------------------------------------
Betula papyrifera Renaissance Oasis Birch 40 30 24 32
---------------------------------------------------------------------------------------------------------------------------------------------------
Betula papyrifera Prairie Dream Birch 40 30 24 32
---------------------------------------------------------------------------------------------------------------------------------------------------
Carpinus betulus Emerald Avenue Hornbeam * 35 25 15 20
---------------------------------------------------------------------------------------------------------------------------------------------------
Carpinus betulus Frans Fontaine Hornbeam * 35 15 15 20
---------------------------------------------------------------------------------------------------------------------------------------------------
Carpinus caroliniana Native Flame Hornbeam 30 20 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Celtis occidentalis Magnifica Hackberry 50 40 30 40
---------------------------------------------------------------------------------------------------------------------------------------------------
Cercidiphyllum japonicum Katsura 40 40 20 27
---------------------------------------------------------------------------------------------------------------------------------------------------
Cladrastis kentukea Yellowwood 30 40 30 40
---------------------------------------------------------------------------------------------------------------------------------------------------
Cornus hybrid Venus Dogwood 25 20 20 27
---------------------------------------------------------------------------------------------------------------------------------------------------
Cornus kousa Aurora Dogwood 24 20 20 27
---------------------------------------------------------------------------------------------------------------------------------------------------
Corylus colurna Turkish Hazelnut 50 25 20 27
---------------------------------------------------------------------------------------------------------------------------------------------------
Crataegus crus-galli Thornless Cockspur Hawthorn * 25 25 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Crataegus x mordenensis Toba Hawthorn * 20 20 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Crataegus phaenopyrum Washington Hawthorn * 25 20 12 16
------------------------------------------------------------------------------------------------------------------------------------------------------------------
Eucommia ulmoides Emerald Pointe Rubber Tree 45 45 24 32
------------------------------------------------------------------------------------------------------------------------------------------------------------------
Fagus sylvatica Fastigate Beech 45 15 36 48
---------------------------------------------------------------------------------------------------------------------------------------------------
Fagus sylvatica   Rivers Purple Beech 50 40 40 53
---------------------------------------------------------------------------------------------------------------------------------------------------
Ginkgo biloba   Presidential Gold Ginkgo 50 40 36 48
---------------------------------------------------------------------------------------------------------------------------------------------------
Ginkgo biloba   Princeton Sentry Ginkgo * 40 15 36 48
---------------------------------------------------------------------------------------------------------------------------------------------------
Gleditsia triancanthos Shademaster Honeylocust * 45 35 30 40
---------------------------------------------------------------------------------------------------------------------------------------------------
Gleditsia triancanthos Skyline Honeylocust * 40 40 30 40
---------------------------------------------------------------------------------------------------------------------------------------------------
Gymnocladus dioicus Expresso Kentucky Coffee Tree 50 35 40 53
---------------------------------------------------------------------------------------------------------------------------------------------------
Halesia monticola   Mountain Silverbell 40 25 18 24
---------------------------------------------------------------------------------------------------------------------------------------------------
Koelreuteria paniculata Summerburst Goldenrain Tree 30 30 15 20
---------------------------------------------------------------------------------------------------------------------------------------------------
Liquidambar styraciflua Rotundiloba Sweetgum 45 25 18 24
---------------------------------------------------------------------------------------------------------------------------------------------------
Liriodendron tulipifera Emerald City Tulip Tree 60 30 48 64
---------------------------------------------------------------------------------------------------------------------------------------------------
Maackia amurensis   MaacNificent Amur Maackia 25 20 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Maclura pomifera inermis White Shield Osage Orange * 35 35 24 32
---------------------------------------------------------------------------------------------------------------------------------------------------
Magnolia hybrid   Galaxy Magnolia 30 10 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Malus sp. Adirondack Crabapple * 18 10 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Malus sp. Prairifire Crabapple * 20 20 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Malus sp. Purple Prince Crabapple 20 20 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Malus sp. Royal Raindrops Crabapple 20 15 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Malus sp.   Zumi Calocarpa Crabapple * 20 24 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Metasequoia glyptostroboides Dawn Redwood 70 25 48 64
---------------------------------------------------------------------------------------------------------------------------------------------------
Nyssa sylvatica Afterburner Tupelo 35 20 24 32
---------------------------------------------------------------------------------------------------------------------------------------------------
Ostrya virginiana   Autumn Treasure Hophornbeam * 40 25 18 24
---------------------------------------------------------------------------------------------------------------------------------------------------
Oxydendrum arboreum   Sourwood 20 15 10 14
---------------------------------------------------------------------------------------------------------------------------------------------------
Parrotia persica   Vanessa Persian Parrotia 30 20 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Phellodendron amurense His Majesty Cork Tree 40 35 18 24
---------------------------------------------------------------------------------------------------------------------------------------------------
Platanus x acerifolia   Exclamation Planetree * 50 40 48 64
---------------------------------------------------------------------------------------------------------------------------------------------------
Prunus serrulata Amanogawa Cherry 20 20 10 14
---------------------------------------------------------------------------------------------------------------------------------------------------
Prunus nigra   Princess Kay Canada Plum 18 12 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Prunus subhirtella Autumn Flowering Cherry 25 22 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Prunus sargentii   Spire Cherry 35 10 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Prunus x yedoensis Yoshino Cherry 30 30 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Prunus x cistena Big Cis Plum 14 12 8 11
---------------------------------------------------------------------------------------------------------------------------------------------------
Pyrus calleryana   Aristocrat Pear * 40 28 18 24
---------------------------------------------------------------------------------------------------------------------------------------------------
Pyrus calleryana   Autumn Blaze Pear * 30 25 18 24
------------------------------------------------------------------------------------------------------------------------------------------------------------------
Pyrus calleryana   Chanticleer Pear * 40 15 18 24
---------------------------------------------------------------------------------------------------------------------------------------------------
Pyrus calleryana Redspire Pear * 35 25 18 24
---------------------------------------------------------------------------------------------------------------------------------------------------
Quercus acutissima   Sawtooth Oak 40 40 40 53
---------------------------------------------------------------------------------------------------------------------------------------------------
Quercus bicolor   Swamp White Oak * 45 45 40 53
---------------------------------------------------------------------------------------------------------------------------------------------------
Quercus robur   English Oak 50 40 40 53
---------------------------------------------------------------------------------------------------------------------------------------------------
Quercus robur hybrid Crimson Spire Oak 40 20 40 53
---------------------------------------------------------------------------------------------------------------------------------------------------
Quercus ellipsoiedalis Northern Pin Oak * 60 45 52 70
---------------------------------------------------------------------------------------------------------------------------------------------------
Robinia pseudoacacia Purple Robe Locust * 50 32 48 64
---------------------------------------------------------------------------------------------------------------------------------------------------
Robinia pseudoacacia Twisty Baby Locust * 18 18 24 32
---------------------------------------------------------------------------------------------------------------------------------------------------
Sassafras albidum Sassafras 40 30 30 40
---------------------------------------------------------------------------------------------------------------------------------------------------
Sophora japonica Regent Japanese Pagoda tree 50 45 36 48
---------------------------------------------------------------------------------------------------------------------------------------------------
Stewartia pseudocamellia Japanese Stewartia 20 15 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Styrax japonicus Snowcone Snowbell 25 20 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Syringa pekinensis China Snow Tree Lilac 20 20 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Syringa reticulata Ivory Silk Tree Lilac * 20 15 12 16
---------------------------------------------------------------------------------------------------------------------------------------------------
Taxodium distichum Shawnee Brave Bald Cypress 55 20 40 53
---------------------------------------------------------------------------------------------------------------------------------------------------
Tilia americana Boulevard Linden * 50 25 36 48
---------------------------------------------------------------------------------------------------------------------------------------------------
Tilia americana   Redmond Linden * 35 25 36 48
---------------------------------------------------------------------------------------------------------------------------------------------------
Tilia cordata   Greenspire Linden * 40 30 24 32
---------------------------------------------------------------------------------------------------------------------------------------------------
Tilia tomentosa   Sterling Linden * 45 35 30 40
---------------------------------------------------------------------------------------------------------------------------------------------------
Ulmus americana   Princeton Elm * 60 40 45 60
---------------------------------------------------------------------------------------------------------------------------------------------------
Ulmus hybrid   Accolade Elm * 70 60 45 60
---------------------------------------------------------------------------------------------------------------------------------------------------
Ulmus hybrid   Commendation Elm * 60 50 40 53
---------------------------------------------------------------------------------------------------------------------------------------------------
Ulmus hybrid Frontier Elm * 40 30 30 40
---------------------------------------------------------------------------------------------------------------------------------------------------
Ulmus hybrid Triumph Elm * 55 45 45 60
---------------------------------------------------------------------------------------------------------------------------------------------------
Zelkova serrata Musashino Columnar Zelkova * 45 35 24 32
---------------------------------------------------------------------------------------------------------------------------------------------------
Zelkova serrata Village Green Zelkova * 40 40 24 32

The asterisk (*) denotes trees that are extremely tough and will tolerate most urban soils.   All other trees will do well in suburban soil locations and urban sites with improved soil.

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 .5 CEUs toward Certified Arborist, Municipal Specialist, 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 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.

                                                          Marcescence
                                                                             Edited by Len Phillips

Why do some deciduous trees hold on to their leaves all through the winter and most others go completely bare? This retaining of dead leaves and other plant parts, is called marcescence (pronounced mar-ses-cents). 'Marcescence' comes from the Latin 'marcere', meaning 'to wither' and any foliage retained will be the dried autumn foliage. Marcescent leaves are found on some smaller trees or on the lower branches of larger trees. Botanists do not know whether marcescence provides a detriment or competitive benefit to certain trees.

Species
Marcescence is most common with many of the oak (Quercus), beech (Fagus), hornbeam or muscle wood (Carpinus), witch hazel (Hamamelis), hophornbeam or ironwood (Ostrya), and some but not all species of willows (Salix).   Many other trees may have marcescent leaves in seasons where an early freeze has killed the leaves before the abscission layer completed development. Marcescent leaves of pin oak (Quercus palustris) start the development of their abscission layer in autumn and finish in the spring. The base of the petiole remains alive over the winter.

Evolution
To understand why marcescence might develop, consider the evolutionary history of trees. Conifers were the first trees on the planet. Populations of these earliest evergreen trees encountered changing soils and climate as they expanded their range. As evolution continued, trees began to develop different ways of growing and shedding their leaves. This is when the broad-leafed hardwoods evolved.

Evergreens have an advantage because they have the maximum time in a year for its leaves to grow and remain photosynthetic. An additional advantage occurs with the reduced nutrient losses associated with the dropping of leaves that hardwoods encounter.

With these exceptions set aside, all living trees shed some of their leaves at some time. Every leaf has a life span and will fade and fall from the tree at some regular interval. However there is great variation in the timing of this leaf drop. At one end of the spectrum are the evergreens. Though they appear to be fully leafed all of the time, evergreen leaves are not always green and some needles die, turn brown, and fall from the tree after two or three years.

On the other end of the spectrum, you will find deciduous or hardwood trees, which seem to drop their leaves all at once every autumn. In autumn, the cells at the interface between the twig and the end of the leaf stem release enzymes that form an abscission layer which separates the leaf from the vascular bundles, allowing the leaf to fall free. Leaf drop benefits deciduous trees by reducing water loss in winter and allows them to efficiently develop leaves the following spring. The leaf drop in autumn also allows broad-leafed trees in seasonally changing environments to reduce frost, snow, and ice damage during unfavorable seasons while using their broad leaves to increase their photosynthetic efficiency during the warm seasons.

In between the evergreens and broad-leafed trees there is a third class of trees that seem to represent a middle ground of sorts between evergreen and deciduous. Their leaves die in autumn, but many leaves do not fall to the ground when they die. These are the marcescent species listed above. Marcescent leaves may be retained indefinitely and do not break off until mechanical forces such as the wind cause the dry and brittle petioles to snap.

Another class in the spectrum of trees are the palms. Many palms form a cone of leaves under new growth that may persist for years before being released. In some species only juveniles retain dead leaves and the marcescence in palms is considered a primitive trait.

Reasons for Marcescence
The fact is, nobody really knows the reason for marcescence. Botanists do know how it occurs but can only speculate on why it occurs. The abscission layer, separating a leaf and its twig, is formed in autumn. This shuts the leaf off from its life support, causing it to drop. The abscission layer is not fully formed with marcescent leaves. Why, is not known.

Botanists have speculated some reasons for why marcescence occurs. The following is a list of potential reasons:

forest conditions hinder smaller trees and the reduced sunlight slows the abscission process,
sometimes, early cold weather or frosts in autumn may interrupt the abscission process or “kill” leaves quickly. In these cases, the occurrence of marcescent leaves may increase,
the buds hidden by clusters of dead leaves do not get eaten and thus live to become new shoots and leaves in the spring,
marcescence may be helpful to trees living in dry, cold, deer-infested environments,
dead marcescent leaves may deter the feeding by large herbivores, such as deer and moose, which normally eat the twigs and their nutritious live buds,
dead, dry leaves make the twigs less nutritious and less palatable. The protein content of beech and hornbeam twigs is about equal to the leaves; however, the lignin content is a lot higher in the leaves,
marcescent leaves may protect some species from water or temperature stress,
the marcescent species are still evolving to become fully deciduous trees from their evergreen past and have not yet mastered being deciduous,
diseases or pests have killed the leaves before they can develop an abscission layer,
cold autumn temperatures slow the photosynthetic process and the leaves hang on the tree into the winter,
some marcescent leaves have been confirmed to improve survival, help the tree's water balance, and protect the tree from cold injury,
the retained leaves, particularly on young trees and the lower branches on bigger trees, is an effective means of trapping snow like a fence, leading to more moisture at the base of the tree when growth resumes in the spring,
marcescent leaves provide shelter for wintering birds as they perch among the rattling leaves, away from winter’s wind,
the persistent leaves might provide some frost protection for buds and new twigs to assist in survival over winter.
some ecologists suggest that marcescence provides an advantage for trees growing on dry, infertile sites. The beech and oak grow well and faster than other species. The retained leaves means a delay in the decomposition of the leaves and that dropping them in spring delivers organic material at a time when it is most needed by the growing parent tree. Even small amounts at the right time could shift the competitive advantage toward these species on poor sites.

Conclusion
While physiologists and botanists agree that marcescence is a juvenile trait, most commonly observed on young trees and on lower branches, there is considerable debate about why some species would seem to be deciduous in all other aspects except that they delay the physiological process of leaf shedding.

Regardless the reason for marcescent leaves, when growth begins next spring the expanding buds will push them off and new leaves will appear on the branches. Until that happens, enjoy the waving brown leaves and the texture they add to the forest and the winter landscapes.

Sources

Finley, Jim, “Winter Leaves that Hang On”, Penn State Extension, 2012.
NaturePods, “Lingering Leaves – Marcescent Foliage”, NaturePods, January 21st, 2011.
Snyder, Michael, “Why Do Some Leaves Persist On Beech and Oak Trees Well Into Winter?”, Chittenden (Vermont) County Forester, Northern Woodlands, 2010.

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 .5 CEUs toward Certified Arborist, Utility Specialist, Municipal Specialist, Tree Worker Specialist, Aerial Lift Specialist, 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 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.

                                                          Cultivars of Silverbell
                                                                         Edited by Len Phillips

Silverbell has bell-shaped flowers that bloom in late spring. It is attractive as a tree for naturalized garden areas or as a graceful addition to a narrow tree lawn or a small yard. The description that follows provides a summary of similarities that all the cultivars possess.

Species Name:        Halesia
Height:                     20' - 40'
Spread:                    15' - 35'
Bloom Period:         Spring, blooms last about one week
Flower:                     One half inch long bell-shape in 2 – 5 flower clusters
Fruit:                         Persistent, dry, light brown drupe
Summer Foliage:     Dark green in summer, 3" - 5" long
Autumn Foliage:      Yellow in autumn, leaves drop early
Winter Color:           Bark is a major feature in winter
Bark:                          Brown to black, ridged and furrowed, scaly plates
Habitat:                      Species native to Southeastern US
Culture:                      Rich, well drained, moist, acid, high organic soil, sun or partial shade, pH 5 – 6
Growth Rate:             Medium, 12' in 8 years
Pest Problems:         No diseases or pests
Planting:                    Transplants readily
Pruning:                     Prune dead and diseased branches at planting and 3 years later to mature form
Propagating:             Stratified seed or softwood cuttings in summer
Other Comments:     Best used with an evergreen background, seldom needs pruning, low branching tree                                     with ascending branches, low rhododendrons and azaleas grow well under Silverbells

The following Silverbell cultivars are this editor's opinion of the best for growing in the city.

Arnold Pink Silverbell Halesia carolina ‘Arnold Pink’ – Shape: Oval; Foliage: Medium green; Fall Color: Yellow; Flower: Pink.
     In spring, the branches are lined with pendulous, rose pink flowers which fade to a soft pale pink. Introduced by Arnold Arboretum. Fact Sheet

Crushed Velvet™ Silverbell Halesia carolina ‘JFS-PN2Legacy’ – Shape: Oval; Foliage: Bluish green, textured; Fall Color: Yellow; Flower: White.
     Reminiscent of crushed velvet fabric, bluish green leaves with a wavy texture inspired the naming of this compact form of the native Silverbell. The smaller leaf size and fine textured branching combine with the velvety foliage to create a plush appearance. Fact Sheet

Mountain Silverbell Halesia carolina monticola – Shape: Ascending branches form a conical to rounded crown; Foliage: Medium green; Fall Color: Yellow; Flower: White.
       Clusters of snow white bell shaped flowers borne on pendulous stalks appear in May. They are best seen when this tree is planted where it can be viewed from below. Similar to Carolina Silverbell, but with bigger flowers and larger mature size. Fact Sheet

Rosy Ridge Silverbell Halesia carolina ‘Rosy Ridge’ – Shape: Broadly oval; Foliage: Dark green; Fall Color: Yellow; Flower: Pink.
       A little faster growing with slightly deeper colored foliage and flowers, this cultivar has a somewhat bolder appearance than ‘Arnold Pink’. A native tree selection made by Hawksridge Farms of North Carolina.
Fact Sheet

Wedding Bells Silverbell Halesia carolina ‘UConn Wedding Bells’ – Shape: Oval; Foliage: Medium; green; Fall Color: Yellow; Flower: White, prolific.
       Slightly more compact and heavier flowering, this is an ideal landscape Silverbell. Flowers are larger than typical and are borne prolifically along the branches. Fact Sheet

Sources
This information has been gathered from personal observations of the author, living in Massachusetts, Zone 6, and information provided by J. Frank Schmidt & Son.

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 .5 CEUs toward Certified Arborist, Municipal Specialist, Tree Worker Specialist, Aerial Lift Specialist, 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 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.

                                                    Complete Streets Movement
                                                                         Edited by Len Phillips

The Complete Streets movement is reshaping urban boulevards, small towns, main streets, and rural highways. Complete Streets is a program designed to slow cars down, plant trees, and rework roads to accommodate bicyclists, transit users, and pedestrians. This includes people pushing baby strollers and the handicapped in wheelchairs. The program also encourages the elimination of traffic signals and replacing them with all-way stop signs. The goal is to make the downtown easier and more comfortable to walk through.

Studies have shown that the more trees and an attractive, pedestrian friendly downtown, the more time shoppers will spend in the local downtown businesses. Tourism will also increase dramatically. Promoting foot traffic is the catalyst for these big improvements. Protected bicycle lanes is also a major goal of this program.

This program shows that the city is trying to improve the urban environment and encourage a safe downtown. It is suppose to let people know that the streets are not built just for cars and trucks.

As of October 2015, more than 700 cities in the U.S. have committed to the Complete Streets movement.

Factors
There is no definitive template for what makes a Complete Street, but there are many common elements.

Bike lanes – especially those separated from automobile traffic are an essential element. They are defined with curbs, planters containing small trees, and other barriers instead of just painted lanes on the roadway.

Wider sidewalks – make it easier and safer for pedestrians to walk, pass each other, look at business window displays, and allow local restaurants to have sidewalk seating.

Large sidewalk bulges at intersections – provide a shorter walking distance for pedestrians walking across the street and encourage drivers to slow down because of the narrower intersecting street. In some situations, trees may be planted within the bulging areas.

Pedestrian islands – provide another safety measure for people to wait for the traffic to stop before completing the crossing of a street.

Transit improvements – especially downtown buses are essential. By installing shelters at the bus stops, passengers can wait in a safe location and not in the middle of the sidewalk. Often a bus bay will make it easier for bus drivers by letting them pull out of the traffic flow when picking up fares.

Traffic lanes – are usually reduced from four lanes to three. The third lane in the middle of the traffic through lanes, allow for left turns. Studies have shown that this left turn lane gets stopped cars out of the way of the moving cars and this actually allows the traffic to flow better.

New tree planting – is included in the reconstruction efforts to implement Complete “green” Streets. Along with the tree planting efforts are large areas of amended soil and the addition of soil cells for proper tree root growth.

Stormwater retention areas – accompany the tree planting and amended soil areas. The focus is on efforts to retain and treat or even eliminate runoff at the source through cost-effective green infrastructure, improving water quality, while also complementing Complete Streets efforts.

Landscaping with Complete Streets
Landscaping elements that help curb stormwater runoff include bioswales, planters, rain gardens, and street trees. These green elements have been found to be important deterrents of unsafe driving and the resulting injuries. In addition, these green elements contribute to a more comfortable and visually interesting environment for all users. When redesigning streets, project managers can include plants and trees, growing in amended soil, to clean the water runoff and manage stormwater at the site. Photo

Traffic calming elements like the trees and planters, landscaped islands, and curb extensions also provide site opportunities for dealing with stormwater runoff, recycling rainwater, bioretention basins, bioswales, rain gardens, infiltration trenches, and phytoremediation programs if necessary.

Numerous trees reduce the heat island effect and offset carbon dioxide while the widened sidewalks and increased pedestrian features make the street friendlier to those walk on the sidewalks. Such improvements complement the Complete Streets program.

Complete Streets policies are an essential tool in providing transportation choices beyond the personal automobile. Walking and bicycling for the shortest trips, rather than taking a car, could reduce carbon dioxide emissions.   The main principle of the urban street design is that streets are public spaces and they belong to the people. Therefore they should be designed with people in mind.

To learn more about Complete Streets visit Smart Growth America.

Sources

Vock, Daniel C., “Roads for All”, Governing, October 2015.
Smart Growth America website, 2015. http://www.smartgrowthamerica.org

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 .5 CEUs toward Certified Arborist, Municipal Specialist, 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 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.