LA Course #GCE-1-1601
How To Have Better City Trees
Written and/or Edited by Len Phillips & Richard W Gibney RLA/ISA
Sections Go directly to the section by clicking on the title below
How To Have Better City Trees
Written and/or Edited by Len Phillips & Richard W Gibney RLA/ISA
Sections Go directly to the section by clicking on the title below
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:
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 CityGreen, 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
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.
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. The information found on this Northern Tree website was assembled through a grant from the USDA Forest Service Northeast Region in cooperation with Rutgers University and University of Florida.
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:
Enacting a species diversity plan implies three simple actions:
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. The information found on this Northern Tree website was assembled through a grant from the USDA Forest Service Northeast Region in cooperation with Rutgers University and University of Florida.
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 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.
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:
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.
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 Surface Name Spread Trunk (in) Area (sf)
---------------------------------------------------------------------------------------------------------------------------------------------------
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 * photo 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 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 Tree 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 Hazel 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 Espresso 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
Species Trade Height (ft) Crown Diameter Surface Name Spread Trunk (in) Area (sf)
---------------------------------------------------------------------------------------------------------------------------------------------------
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 * photo 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 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 Tree 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 Hazel 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 Espresso 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 test that follows contains 30 questions. Before taking the test be sure you have read the article carefully. The passing grade is 80% on the entire test.
LA CES will award 1.0 PDH (HSW) credit for a passing grade. North Carolina Board of LA and New Jersey Board of Architects have approved this course for 1.0 credits.
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