10-03-99 Checking Tree Safety Before Winter Storms

Checking Tree Safety Before Winter Storms

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Mary Robson (Ret.), Area Extension Agent
Regional Garden Column October 3, 1999

Autumn's approach brings concern about potential storm damage to trees, particularly as gardeners and landscapers contemplate the nasty weather conditions of recent winters. Vicious winds and ice storms, or heavy wet snow, have caused severe tree losses and property damage throughout the Puget Sound region. This is the first of two columns on tree hazards.

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.

To help gardeners look for hazard trees with a critical and more educated view, an experienced arborist from Pierce County has contributed to this column. Dennis Tompkins, a certified arborist, brings years of experience in managing trees to his suggestions. Arborists have received special training in tree care and diagnosis, and their help is vital when tree questions arise.

Mr. Tompkins developed this checklist for his tree care clients:

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

Falling trees in the neighborhood:

One very common reason for a tree to fall is because of some type of root problem. Two of the most common are laminated root rot and armillaria root rot. 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.

Laminated root rot is a fairly common root disease that attacks Douglas-fir, hemlock, noble and grand fir throughout the Pacific Northwest. It is spread by root to root contact and can persist in stumps for over 50 years. The fungus often infects groups of trees and is difficult to detect. It is most easily observed, especially if you have some professional help, in the roots of fallen trees.

Armillaria root rot can attack the same tree species listed above, as well as western red cedar. Signs of the disease include oozing of sap from the lower trunk, or a white fan-shaped fungus under the bark. You may notice, upon digging around the roots, the presence of small, black, stringy growths sometimes referred to as "shoestrings." They are fungal "rhizomorphs" around the roots and are difficult to see because they resemble roots.

Roots that have decayed from these or other 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 these 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 on slopes are obviously susceptible to being downed by slope slippage from mud slides. 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 your 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 do not "look happy" are fairly easy to detect.

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. As much as we love our trees, sometimes removal is the best route for peace of mind and safety. Next week, we'll discuss how construction and logging activities may cause tree hazards.

Dennis Tompkins is a Certified Arborist (d.b.a. The Evergreen Arborist), living in Sumner, Washington. He serves as an urban forester and consultant to the Christmas tree industry, provides home consultations, and speaks to organizations in the lower Puget Sound area.

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