Landscape - Assessing Potential for Winter Storm Damage to Trees

With fall progressing, it brings to mind concerns about potential storm damage to trees. Vicious winds and ice storms, or heavy wet snow, have caused severe tree losses and property damage in the past. The following are some considerations in assessing potential for winter storm damage to trees.

It's often difficult to predict what will happen to trees in landscapes during storms. Healthy trees with no apparent potential problems can drop limbs or fall entirely during unusual weather. But the more common hazards from tree damage occur with trees that are unhealthy or stressed. If a tree has dropped big branches, or shows signs of interior rot when a branch falls, it definitely should be checked.

If a tree has a likelihood of falling, and has a target to hit if it falls, it may be considered a hazard tree.

Checklist for tree hazards:

1) Is there a history of trees falling near your home during bad storms?
2) Do certain trees look unhealthy compared to their neighbors?
3) Has there been construction activity near your trees in recent months or years?
4) Has nearby logging changed the growing conditions and exposed remaining trees to less shade, or stressed them in other ways?

Falling trees:

One very common reason for a tree to fall is because of some type of root problem. Consulting a qualified tree care professional makes good sense if you suspect the presence of a root disease, or if there have been many falling trees in your immediate neighborhood.

Roots that have decayed from fungi may no longer adequately anchor a tree. High winds combined with saturated ground may cause tree failure when root disease has developed.

Unfortunately, finding no signs of root diseases does not mean they are not present. However, close inspections of roots and trunks of fallen trees or drilling suspect trees to look for interior decay can be done by Certified Arborists and/or urban foresters that are familiar with root rots. Professional hazard evaluations are highly recommended for trees located near those that have died, fallen or appear to be dying.

Generally, roots aren't removed when hazard trees are cut down. If a root rot disease has been present, be certain not to replant susceptible trees in the same area.

Tree fall can also be caused by factors other than root rots. Trees may be rocked over by wind when soils are saturated with water. So in addition to root rot problems, there will be other possibilities checked by arborists when evaluating whether a tree is a hazard.

Checking trees for healthy appearance:

If you were to glance around at the trees in a neighborhood, the crowns will range from those with lush, full, healthy appearing foliage to those that have sparse, poor colored foliage. The crown is the part of the tree at the top, the branches that you see silhouetted against sky. The branch pattern and foliage pattern at the top of the tree will be the first area to show symptoms of tree disease. Trees that

With deciduous trees (those that drop their leaves in fall), such as maples, check for crown health when the trees still have all their summer leaves, before leaves begin to drop. The apparent thinning of leaf and twig health at the top of a deciduous tree is much more difficult to detect during and after leaf fall.

Often, a tree in distress will leaf out later than usual in the spring and have smaller leaves than are common. It may also set a very large, bountiful crop of seeds, though seed set needs to be looked at along with other factors in the tree.

Once a large tree begins to show severe symptoms, the situation isn't reversible. There generally are no cures for conifer trees that have root problems or that appear to be dying. Get advice from a qualified professional arborist.

Adapted from "Checking Tree Safety Before Winter Storms" by Mary Robson (Ret.), Area Extension Agent Regional Garden Column October 3, 1999, Washington State University.