Tuesday, June 16, 2009

Landscape - Reducing Storm Damage in Trees

After the recent violent storms in Delaware and significant damage in landscapes, I thought it would be good to repost an article on preventing storm damage to trees.

There is no way, except for complete enclosure, to protect trees from all storm damage. Trees are not adapted to worst-case storms -- only to our average wind climate. Listed are several things to minimize the main types of storm damage:

Let trees adjust to the wind environment. Tight staking and guying from the time of planting holds a tree in place while preventing internal adjustment to wind loading. Always stake and tie the tree loosely where the stem can move and bend in the wind. Keep ties in place for a few growing seasons to ensure a well-established root system. Continue to loosen and, eventually, release the ties. Leave the support stakes in place to protect the stem from mechanical damage. After five to seven years, remove all tree support. The tree will continue to grow and adjust to its new environment.

Practice proper pruning techniques by cutting branches before they become larger than 1 inch in diameter. Do not damage the branch collar (Figure 1). The branch collar is part of the stem and, if damaged by poor pruning, provides an avenue of attack into the main stem for pests. Proper pruning minimizes a number of structural problems that occur in association with new wood growth around a pruned branch.

Eliminate co-dominant branches. Prune forked branches and branches that arise opposite each other on the stem early. Cut one side off now to prevent loving the whole tree later if it splits in a storm. In trees with opposite branching patterns (such as ash or maple), proper branch training is essential for a long-lived, storm resistant tree.

Keep trees as healthy as possible with timely watering and proper fertilization. Healthy, vigorous trees adjust more quickly to changes in the environment, are more wind firm and react more effectively to damage.

Do not over-fertilize the tree with nitrogen or over-water the soil. This can increase the crown surface area and/or decrease the rooting area. This type of biological change makes the tree susceptible to storm damage.

Eliminate lopsided crowns. Prune branches to produce a reasonably symmetrical crown. If more than 70 percent of the crown is on one side of a mature tree, consider tree removal and replacement. Guying and bracing branches are last-ditch efforts when a tree has to be saved in spite of itself.

Remove or treat pest problems such as branch cankers to minimize potential damage. Do not over-treat tree hollows. Do not remove decayed wood from hollows unless it falls away in your hands. Cleaning hollows can lead to further internal damage. Cover the openings to hollows to allow the tree to grow over the opening; covering also prevent animals from expanding the hollow and keeps water from running in.

Keep the tree growing upright with one main stem. Prune away branches that compete in height with the main stem. Eliminate branches with tight or narrow crotches.

Install lightning protection systems on historic, rare, specimen or recreational area trees. Consult a qualified arborist or urban forester to ensure adequate design. Lightning protection systems are covered in detail in the section "Lightning Protection Systems."

Continue to promote wind firmness by not over-crowding trees and by proper guying and bracing. A tree must always be able to move in the wind. Do not keep a tree tied into position with tight cables. In a stand of trees, slowly remove trees over a number of years to allow wind firmness to develop in the remain-ing trees.

Information from "Storm Damaged Trees: Prevention and Treatment" by Kim Coder, Professor Silvics/Ecology, Warnell School of Forest Resources, University of Georgia. Go to http://pubs.caes.uga.edu/caespubs/pubcd/C806.htm for the full fact sheet.

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