Hundreds of thousands of trees are planted along city and community streets and on other public property throughout the United States each year. Unfortunately, many of these trees, perhaps 50 percent or more, do not survive beyond one or two years. Why?
Transplant Shock
Most newly planted trees are subject to stress-related problems due to tremendous root loss when dug at the nursery. This condition, commonly called transplant shock, results in increased vulnerability to drought, insects, diseases and other problems. To a greater or lesser degree, transplant shock lasts until the natural balance between the root system and the top or crown of the transplanted tree is restored. Of those newly planted trees that do not survive, most die during this root-establishment period. A tree’s chance of survival can be drastically improved through practices that favor establishment of the root system. This involves regular care during the first three years following transplanting.
Tree Roots and Transplanting
For an undisturbed, healthy tree, the root system is normally very shallow. Even the major structural roots grow almost horizontally. The root system normally extends far beyond the branch spread, and fine roots that absorb water and nutrients are located very near the soil surface, usually in the top four to ten inches. A natural balance exists between the roots (where water is absorbed) and the top of the tree (where water is utilized and transpired to the atmosphere).
Usually when a tree is dug for transplanting, more than ninety-five percent of the absorbing roots are severed. With less than five percent of its root system remaining, the newly transplanted tree suffers from water stress. The crown is capable of losing water faster than it can be absorbed by the limited root mass. Water stress, in turn, can reduce the ability of leaves to produce carbohydrates (energy), diminish the growth of all parts of the tree, and subject the tree to many other environmental and pest-related problems. Combined, these problems all contribute to "transplant shock" that can kill the tree.
Generating Root Systems of Newly Planted Trees
Successfully establishing a transplanted tree depends primarily on rapid root generation. However, keeping the top of the tree alive and healthy until the natural balance between the roots and top is restored is essential. Initial root development of a newly planted tree is supported by energy (carbohydrates) stored within the trunk, branch, and root tissues. Continued root growth during the establishment period depends on the leaves of the tree producing high levels of carbohydrates during the growing season, especially during the first year following transplanting.
For this reason, pruning transplanted trees to compensate for root loss is not recommended. Leave the entire top intact to favor rapid development of a supporting root system. Top pruning should be restricted to removing broken and damaged branches and developing a good tree structure. Supplemental watering is critical to avoiding moisture stress.
The length of the tree-establishment period depends on both the size of the root system prior to digging and on having conditions that are favorable for good root growth. Larger trees may lose a larger mass of roots than smaller trees and require a longer root-establishment period. Adapted from :
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Forestry Leaflet 17 Revised January 1999 |