Best Management Practices for
Successful Urban Tree Plantings

Best Management Practices for Successful Urban Tree Plantings
SITE EVALUATION AND DESIGN CONCERNS
Best Management Practices (BMPs) for successful landscape tree establishment in the urban environment depends on the design, site analysis, tree species selection, and proper planting and maintenance. All these factors are interrelated. Compromises to any of the BMPs are cumulative and affect other establishment factors. Successive compromises result in stress to the tree with potential death or failure of the planting. Each factor will be highlighted separately but keep in mind that all factors are evaluated with attention to each other.

Evaluation of the site to develop the design is the first step in a tree planting program. Once you know the restraints of the site and the design requirements, plants can be selected and planting and maintenance specifications written to meet the site limitations. The following points should be considered during the site evaluation and design process:

  • The USDA hardiness zones for Alabama are Zones 7 and 8. Hardiness is not as big a concern as tolerance to heat and low chilling hours or photoperiod required for proper bud set of some tree species.

  • Is irrigation available?

  • What is the light exposure, sun or shade?

  • What is the soil nutrition analysis, especially pH, phosphorus and potassium? These nutrients are better adjusted according to the soil test prior to planting.

  • What is the internal soil drainage? Test by digging a hole 18 inches deep and filling it with water. If water is gone in 1 to 2 hours, the soil is well drained; 12 to 24 hours, soil drainage is moderate; more than 24 hours, soil drainage is poor.

  • What is the distance to the soil water table? Dig a hole 2 feet deep and wait 2 to 3 hours to see if water fills the hole. If water appears in the hole, there is a high water table. Is there a hard pan that limits drainage or is it a high water table?

  • Is the soil texture clay, loam or sandy?

  • Is the soil density compacted/hard or loose?

  • Will your trees be planted in an open park setting, a sidewalk tree cut or a planting strip? What are the dimensions of the root zone space and volume of soil available for tree growth?

  • Is there a swimming pool, septic tank, vegetable garden, annual planting bed within 50 feet of the planting area?

  • What is the distance between the tree planting and any building?

  • Are there underground or aboveground utilities or lights that need to be considered?

  • Be sure trees are sited far enough back from an intersection or sidewalk and are limbed-up enough to prevent obstruction of views of passing motorists and allow for safe pedestrian traffic on sidewalks.

  • Is there a budget for pruning and maintenance of the trees?

  • Are there landscaping or tree ordinances that would affect selection and size of trees?

  • What is an assessment of tree diversity in the area?

  • Are the trees to be used for a screen, shade or a focal point?

  • What trees currently exist in the planting area? What construction activities have recently gone on that might impact these trees? Are they healthy, desirable trees?

  • What is the size, shape, texture, color, evergreen/deciduous requirements of the trees needed for the design?

  • Are there storefronts, signs, traffic vision concerns or other views that may need to be considered in the selection of the trees?

Best Management Practices for Successful Urban Tree Plantings
SPECIFICATIONS FOR TREE SELECTION
Successful landscape plantings can only occur when high quality nursery stock is selected which has the proper limb structure and root/shoot ratio balance. Trees should be healthy, free of disease and insect pests, and the quality should be maintained during transportation from the nursery and throughout the planting process. The following check list offers “minimum” guidelines for selection of trees for the landscape.

Shade trees should:

  • Have a strong, straight central leader with no lateral branches greater than 2/3s the caliper of the main leader.

  • Have branches equally spaced around the central leader at least 6 inches apart. Each branch should have its own space.

  • Have a uniform canopy in shape from all sides and free of large voids.

  • Have trunks which are free from all cuts and scratches. There should be no more that 40% of the height which is clear of branches unless it is specified by the designer.

  • Have proper pruning cuts that are not flush cuts but pruned to the collar.

  • Have been root-pruned and irrigated during production for a better root system.

  • Have root balls in B&B plantings which are of the appropriate size (see below) and they should be firm with no loose movement between the trunk and the root ball when the trunk is rotated.

  • Have roots at the interface of the burlap and soil.

  • Have container roots which fill the entire container without having any root greater than 1/5 the tree caliper and no large roots in the upper 3 inches of media encircling more than 1/3 of the root ball. If kinked roots are less than 1/3 of the root ball, they can be pruned.

  • Have tree branches with good spacing and wide angles from the main trunk with no included bark.

  • Be smaller rather than larger. Plant 1.5 to 3.5 inch caliper trees unless instant effect is desired and good soil conditions permit a large planting. Smaller trees establish better in poorly drained, low oxygen soils.

Standards for Various Container and Field Grown B&B Trees
The following tables, taken from the American and Florida Standards and Grades for Nursery Stock, offer a guide to the MINIMUM acceptable industry standards for root balls and container sizes for field and container grown trees. When selecting trees from the nursery, be sure that the nursery stock meets or exceeds these guidelines.

ROOT BALL SIZE STANDARDS
Trunk caliper
(inches)
Minimum ball
diameter on
field grown
shade trees
Minimum
root ball
diameter on
fabric
container
grown trees
Minimum
container
size (gallons)
Minimum tree
height on
standard trees
Minimum tree
height on
slower grown
trees
Maximum
tree height
1 16 12 5 6 5 10
2 24 18 20 10 8 14
3 32 20 45 12 9.5 16
4 42 30 95 14 10.5 18
5 54 36 95 . ..
The optimum tree size depending on your need for instant effect and your site requirements should fall between 1.5 and 3.5 inches in caliper.

ROOT BALL DEPTH AND DIAMETER
Root ball diameter (inches)Minimum root ball depth
Less than 20 Not less than 75% of diameter
20-30 Not less than 66% of diameter
31-48 Not less than 60% of diameter
Source: American Standard for Nursery Stock, ANSI Z60.1 published by American Association of Nurserymen, Washington D.C. The complete publication can be found on line at:
http://www.anla.org/applications/Documents/Docs/ANLAStandard2004.pdf. The University of Florida had developed their own grades and standards for minimum container size recommendations for trees grown in aboveground and fabric containers, http://hort.ifas.ufl.edu/woody/planting/americanstandard.htm.

Caliper is measured 6 inches from the ground on trees less than 4 inches in caliper. Above 4 inches in caliper measured at 6 inch height, move to 12 inches above the ground to measure trunk caliper or diameter.

BARE ROOT CALIPER, TREE HEIGHT AND ROOT SPREAD
Caliper (inches) Average height range (feet) Minimum root spread (inches)
.5 5-6 12
.75 6-8 16
1 8-10 18
1.25 8-10 20
1.5 10-12 22
1.75 10-12 24
2 12-14 28
2.5 12-14 32
3 14-16 38
Example: If your tree is 2.5 inches in caliper the average height should measure between 12 and 14 feet and the root spread should be a minimum of 32 inches.

BOX SIZE FOR TREES
Box diameter Maximum caliper range (inches)
20 1.25-2
24 1.5-2.5
30 2.5-3
36 2.5-3.5
42 3-4
48 3.5-5
60 4-6
Source: American Standard for Nursery Stock, ANSI Z60.1 published by American Association of Nurserymen, Washington D.C. The complete publication can be found on line at: http://www.anla.org/applications/Documents/Docs/ANLAStandard2004.pdf. The University of Florida had developed their own grades and standards for minimum container size recommendations for trees grown in aboveground and fabric containers, http://hort.ifas.ufl.edu/woody/planting/americanstandard.htm.

Caliper is measured 6 inches from the ground on trees less than 4 inches in caliper. Above 4 inches in caliper at 6 inch height, move to 12 inches above the ground to measure trunk caliper or diameter.

Best Management Practices for Successful Urban Tree Plantings
PLANTING AND MAINTENANCE SPECIFICATIONS
Best Management Practices (BMPs) for successful landscape tree establishment in the urban environment depends on the design, site analysis, tree species selection, and proper planting and maintenance. All these factors are interrelated. Compromises to any of the BMPs affects other establishment factors and results in stress to the tree with potential death or failure of the planting. Each factor will be highlighted separately but keep in mind that all factors are evaluated with attention to the other three factors.

Once the proper tree has been selected to fit the site and the landscape design, proper planting and follow-up care are required for the success of the project. The following points should be considered during the planting process:

  • Trees are transported to the site in a covered vehicle that prevetns wind and termperature extremes.

  • Plants should be well watered prior to shipping and checked for moisture at arrival.

  • On site plant material is maintained under shade and irrigated twice daily. Plants are healed-in if B&B material is used.

  • Trees should be protected from extreme temperatures, freezing or extreme heat.

  • Always handle tree by the root ball using straps or powered equipment and do not lift using branches or the trunk. The trunk should be wrapped during shipping and the planting process for protection.

  • Inspect roots of container trees and remove any large roots that are circling over 1/3 of the root ball especially in the upper 2 to 3 inches of the root ball. Removing very large roots can result in excessive stress and possible death of the tree.

  • The hole should be dug 2 to 3 times wider than the root ball to allow easy access by the roots into the surrounding soil and no deeper than the root ball.

  • Rough-up or score sides of the hole to prevent glazing or compaction of planting hole and potential obstruction of lateral root growth.

  • Most urban soils are compacted and poorly drained resulting in low oxygen for the roots. Plant the tree with the root ball top at least 1 to 3 inches above the soil line with the trunk flare/root flare and uppermost roots at least level with the backfill surrounding the tree.

  • Soil removed from the hole makes the best backfill unless the whole planting area can be amended uniformly. There is no apparent benefit from root stimulants, water absorbing gels, mycorrhizae or fertilizer at planting. Planting site should be fertilized according to Soil Test recommendations for long term health of the tree.

  • Gradually straighten the tree as backfill is added.

  • Remove synthetic wraps, rope, twine from the tree and ball. Wire baskets should be removed when possible but research and practical application allows for removing at least the top 2 to 3 rungs of the basket. Although wire does not deteriorate, roots grow to encapsulate wire without apparent damage.

  • Slice a shovel or spade around the backfill to settle the soil and remove air pockets. Break up heavy clay clods. Do not step firmly on the backfill which may cause excessive compaction.

  • Irrigate with 10 to 20 gallons of water to the root ball and surrounding soil. Apply 2 to 3 inches of mulch to the edge of the root ball extending 6 to 8 feet from the tree. A thin layer of mulch (1/2 inch) can be applied to the root ball area for aesthetics. Do not pile much against the trunk of the tree.

  • Only a thin layer of mulch and no soil should be on the top of the original root ball allowing the roots surrounding the root ball to be on the surface and water to penetrate into the root ball.

  • Stake the tree if the planting is in a windy area or an area of high traffic. If the tree is leaning due to lack of taper or strength, tree selection was improper. Many trees with heavy root balls do not need staking.

Principles of tree staking

Planting specification

Maintenance Requirements for Successful Tree Planting

  • Trees provided with regular irrigation, 3 times per week, for the first 6 to 8 weeks during the growing season to stimulate greater root growth. Moisture should be monitored carefuly for the remainder of the year. Establishment period is about 6 months for each inch tree caliper (ex. 3” caliper = 18 month establishment period).

  • Two to three gallons of water is required for each caliper inch of tree. Irrigation is applied to the root ball. If root ball is wet, do not irrigate.

  • Pruning should have been done at the nursery. No pruning for the first year after planting. Pruning can inhibit root growth and establishment.

  • Maintain 8’ mulch area surrounding tree and limit traffic to prevent compaction.

  • No grass or weeds are allowed close to the trunk.

  • Inspect planted trees to be sure they were not planted too deep and root flare is distinctly visible.

  • Remember to remove all stakes and guying materials after first year.

  • Pruning is required after year 2 to remove lower limbs to lift canopy and maintain central leader, limb spacing and arrangement of limbs on the central trunk. Proper pruning cuts are required (no flush cuts!).

  • Trees respond to fertility after year one primarily to Nitrogen (N) at a rate of 3 to 5 pounds of N per 1000 ft2. If phosphorus and potassium have been adjusted to a medium level or better, those nutrients should be sufficient.

  • A split application of fertilizer in winter/spring (February/March) and again in mid June should result in maximum growth potential.

  • Sandy soils can benefit from 3 applications for maximum growth using the same rate split into 3 applications in February, late April/early May, and late June/early July.

  • Older trees, one application in February/March.

Best Management Practices for Successful Urban Tree Plantings
SELECTION OF HURRICANE RESISTANT TREES FOR SOUTH ALABAMA URBAN FORESTS
The following list of trees has proven to be either highly or moderately resistant to wind. The list was derived from research and observational data. There are a number of factors that contribute to the damage inflicted by hurricanes. The genus and species of trees are very important for urban tree selection. Trees planted in clumps survive better than those sited as single tree specimens. The duration and intensity of the storm are also obvious factors contributing to the damage. The amount of rain prior to the heavy winds increases the potential damage by loosening the soil around the roots. Road and driveway cuts, compacted, shallow or low aerated soils, poor planting and pruning techniques, soil chemistry incompatibility, and lack of volume of soil are other factors limiting root growth and stability of the trees. Many trees are diseased and unhealthy, have genetically poor branch structure, are weak wooded, and are subject to breakage with low wind intensity. Other trees are physically more open or aerodynamically designed and have lower resistance to the wind and experience fewer problems. Smaller and younger trees generally withstand wind better than larger, older trees.

High to Medium High Wind Resistance
If volume of soil for root growth is limited, small to medium trees should be selected. Small to medium trees offer little damage potential and are better suited to small urban island planting sites. There are many other great trees for the landscape but these trees have been selected for their stability in hurricane areas.

Note: “P” indicates better for park setting with improved soil quality and volume.

High to Medium High Wind Resistance
Acer palmatum Japanese Maple
Amelanchier arborea Downy Serviceberry (P)
Carpinus carolinianaIronwood
Cercis canadensis Redbud
Chionanthus retusus Chinese Fringetree
Chionanthus virginicus White Fringetree
Cornus florida Dogwood (P)
Halesia tetraptera Carolina Silverbell
Ilex cassineDahoon Holly
Ilex opaca American Holly
Ilex vomitoria Yaupon Holly
Ilex x attenuata Foster Holly, other attenuata cvs
Ilex x ‘Fineline’Fineline Holly
Koelreuteria paniculataGoldenraintree
Lagerstroemia indicaCrape Myrtle
Magnolia soulangiana Saucer Magnolia
Pistacia chinensisChinese Pistache
Podocarpus sppPodocarpus
Quercus geminata Sand Live Oak
Vitex agnus-castus Chastetree

Larger Urban Trees
In order to mature to their potential, large trees need room (soil volume) for their roots to expand. A good general rule is for every 1 inch caliper that you envision the tree’s mature growth, you need to provide a minimum of 2 feet for each inch on the side of a square root zone planting area. Example: If you envision a 12 inch caliper tree, the root zone required is 2 feet x 12 inches = 24 feet square or 576 square feet root zone area. Another general rule is you need 15 feet square planting area for a tree to realize its growth potential. Large trees resistant to high or medium winds include:

Large Urban Trees
Acer saccharum subsp. floridanumFlorida Sugar Maple
Betula nigra River Birch
Diospyros virginiana Common Persimmon (P)
Fraxinus americana White Ash
Magnolia virginiana Sweetbay Magnolia
Magnolia grandiflora Southern Magnolia
Nyssa aquaticaWater Tupelo
Nyssa sylvaticaBlack Tupelo (P)
Ostrya virginianaAmerican Hophornbean
Quercus alba White Oak
Quercus laevis Turkey Oak
Quercus michauxiiSwamp Chestnut
Quercus myrtifoliaMyrtle Oak
Quercus schumardiiSchumard Oak
Quercus stellataPost Oak (P)
Quercus virginiana Live Oak
Ulmus americanaAmerican Elm (P)
Conifers
Cedrus deodaraDeodar Cedar (P)
Pinus palustris Longleaf Pine (P) no to shallow soils
Taxodium distichum var. distichum Baldcypress
Taxodium distichum var. nutans Pondcypress
Palms
Butia capitata Pindo
Sabal palmetto Cabbage

Trees with Medium-Low and Low Wind Resistance NOT
to Plant in South Alabama Urban Forests
Dicots
Acer negundoBoxelder
Acer rubrum Red Maple
Acer saccharinumSilver Maple
Albizzia julibrissinMimosa (invasive)
Carya illinoensis Pecan
Celtis laevigata Sugarberry
Celtis occidentalis Hackberry
Eriobotrya japonica Loquat
Fraxinus pennsylvanica Green Ash
Liriodendron tulipiferaTulip Poplar
Morus rubra Red Mulberry
Myrica ceriferaWax Myrtle
Persea borboniaRedbay
Platanus occidentalisSycamore
Prunus caroliniana Carolina Laurelcherry
Prunus serotinaBlack Cherry
Pyrus calleryana Bradford and other pear cultivars
Quercus falcataSouthern Red Oak
Quercus laurifoliaLaurel Oak
Quercus nigra Water Oak
Quercus phellos Willow Oak
Sapium sebiferumChinese Tallow (invasive)
Ulmus americana American Elm
Ulmus parvifoliaChinese Elm
Zelkova serrataJapanese Zelkova
Conifers
Juniperus virginiana var. silicicolaSouthern Red Cedar
Pinus clausa Sand Pine
Pinus elliottii var. elliottiiSlash Pine (P only)
Pinus glabra Spruce Pine (P only)
Pinus taeda Loblolly Pine
X Cupressocyparis leylandiiLeyland Cypress

FACT SHEET: Alabama Cooperative Extension System By Dr. Ken Tilt, Dr. Joe Eakes, David West, James Miles, and William East