Green Horizons

Whether growing in your yard or in high-value plantations, trees are subject to damage by environmental stresses -- including wind or lightning during this time of year, and in a few months, snow or ice. It is important to know when and how to offer aid to a damaged tree to save it from future decay and possible loss.

Evergreen trees, and even deciduous trees that do not shed their leaves, (such as this red oak) are susceptible damage from ice storms.

Wind injury is usually obvious and not difficult to diagnose. Remove the damaged branch just above the limb’s branch collar. The branch collar is the "donut-shaped" ring of growth around the limb as it attaches to a larger limb or the tree’s trunk. If you remove this collar, then the tree cannot naturally close the wound, and you have an entry point for disease organisms and insects. If the damage is high up in the tree, you should call a certified arborist who has the experience and proper equipment to safely remove the affected limb(s).

I usually do not recommend covering the cut with any sort of a dressing (e.g. latex paint, tar or other similar type of wound dressing). It’s sort of like putting butter on a burn, in that it slows the healing process.

The one exception that I do make, however, is in the case where the oak wilt disease is prevalent. Covering the cut surface, in that case, helps prevent sap-feeding insects from infecting the tree with the fungal spores that cause oak wilt.

There are several things that you can do to reduce wind and ice damage to trees:

• Remove branches that have narrow crotch angles.
• Do not over-fertilize with nitrogen, as this stimulates rapid growth with weak wood.
• Do not top your trees, as this sets up a weak union between the old and new growth.

Tree limbs with narrow crotch angles are very susceptible to ice and windstorm damage.

A tree that has been struck by lightning can have many different symptoms. Some trees immediately burst into flames and explode when they are hit; others show no damage until a later time. Typically, strips of bark extending down the trunk or branches are loosened or burned and may hang from the tree. The extent and type of damage determines if the tree will live. It is often a "wait and see" situation. Lightning that completely kills plant tissue around the entire circumference of the tree will prevent translocation of water up the tree, and stop the movement of food produced in the leaves downward to the roots.

Plants covered with ice or snow can be damaged by an increase in weight load. High winds make the situation worse. Due to their year-round foliage, evergreen trees are particularly susceptible to this type of damage. Do not be in a hurry to start pruning a branch that is bent out of shape -- in a few days, it may straighten on its own. Do not try to remove ice from a tree’s limbs, since additional damage due to breakage may occur. If you must remove damaged limbs, follow the same guidelines for wind-damaged trees.