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Classics
The following article has been selected because it is deemed very important to the arboricultural profession
and deserves special recognition.  It has appeared in a previous Seminar and because of this it is not eligible for earning certification credits; there is no test at the end of this article.



                                                       Right Tree - Right Place
                                                                           Edited 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.

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​Species
                                             Trade                                       Height (ft)     Crown    Diameter  Area (sf)  Surface                                              Name                                                           Spread   Trunk (in)   

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