Specifications for Planting Trees and Shrubs in the Southeastern U.S.1 Edward F. Gilman2 Digging the Hole Before digging the hole in well drained soil: 1) Locate the point where the topmost root emerges from the trunk (it should be within the top 2 inches of the ball), and 2) Measure the distance between the topmost root and the bottom of the root ball. Dig the hole about 10% less than this distance and as wide as possible (at least 1.5 times the width of the ball). Remove excess soil to ensure that the topmost root is no more than 2 inches below the surface. Sever circling roots where appropriate. The root ball should be positioned in the hole so the finished grade of the landscape soil is even with or slightly lower than the point where the topmost root emerges from the trunk. Then apply soil or mulch so it covers the sides of the root ball. Be sure that when you are finished planting, there is no landscape soil and little or no mulch placed on top of the root ball. Landscape soil (as well as thick mulch layers more than 1 or 2 inches deep) spread over the root ball can prevent water and air from entering the root ball. When finished planting, the point where the topmost root in the root ball originates from the trunk should be within the top two inches of the root ball. The trunk flare might be visible on some trees depending on age and tree type. In poorly drained soil, position the top of the root ball 10% or more above the surrounding landscape soil. Tip: Never place any soil over the root ball. Fertilization Slow-release (or controlled-release) fertilizer can be applied on top of the root ball and backfill soil or on top of the mulch at planting. There is no need to mix it with the backfill soil or place it at the bottom of the planting hole because most roots end up close to the soil surface in urban and suburban landscapes. Under most circumstances, mulch will not steal the fertilizer from the tree. Adding slow-release fertilizer at planting has not been associated with either improved survival or increased growth after planting. It will not hurt the plant provided it is applied according to the directions on the product. On the other hand, adding soluble fertilizer to a newly installed plant could burn roots if too much is applied. This will injure the plant and could kill it. Any nitrogen source can be applied to established trees with about the same effect. Mulching Weed and turf suppression during establishment is essential. Apply a 3-inch-thick layer of mulch around the plant to help discourage weeds. An area 2 feet in diameter for each inch of tree trunk diameter (minimum diameter should be 8 feet for trees with a trunk diameter less than 3 inches) should be maintained during the establishment period. If you wish to place mulch over the root ball, apply only a thin layer over the outer half of the root ball. This keeps the trunk dry and allows rainwater, irrigation, and air to easily enter the root ball. Mulch resting on the trunk or layered too thick can kill the plant by starving it of oxygen, killing the bark, causing stem and root decay, preventing hardening off, encouraging rodent damage to the trunk, keeping soil too wet, and repelling water. Mulch on the root ball has little impact on water lost from the tree since most of the moisture that leaves the root ball does so by transpiration, not evaporation. Only a small amount (< 10%) leaves the root ball by evaporation from the surface of the root ball. Staking In many instances, if root balls are heavy enough, stakes are not necessary. Stake to stabilize the root ball. Many field-grown trees do not need staking because their root balls are heavy enough to stabilize the tree in the ground. Some container-grown trees will require staking in open areas because root balls are much lighter in weight. Establishment Trees and shrubs provided with regular irrigation through the first growing season after transplanting require about 3 months (hardiness zones 9-11) to 6 months (zones 7-8), per inch of trunk diameter to fully establish roots in the landscape soil. Plants that are under-irrigated during this establishment period often require additional time to establish because roots grow more slowly. Most trees are under-irrigated during the establishment period. Because roots are not fully established, be prepared to irrigate through the entire establishment period, especially in drought. Irrigation Unlike established plants, research clearly shows that recently transplanted trees and shrubs establish most quickly with light, frequent irrigation. For trees planted in spring or summer, provide two (cooler hardiness zones) to three irrigations (warmer hardiness zones) each week during the first few months after planting. Daily irrigation in the warmest hardiness zones provides the quickest establishment. Following the initial few months of frequent irrigation, provide weekly irrigation until plants are fully established. At each irrigation, apply about 2 to 3 gallons of water per inch of trunk diameter (e.g. 4-6 gallons for a 2-inch tree) over the root ball. There is no need to wet the soil outside the root ball in most instances in the eastern U.S. where rainfall is plentiful. There may be a benefit to wetting soil outside the root ball in drier climates. Never add irrigation if the root ball is saturated.