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Garden Tips

AVOIDING HAZARDOUS TREES

GARDEN TIPS – written by Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Written November 29, 2015

You probably have heard about the many trees that came down around our state in the windstorm last week, but you may not have heard about one tree in Spokane that snapped off and speared the house below. It entered the roof, went through the crib of a six-week old baby, and stopped only when it reached the basement floor. Thankfully, the baby was with his mother who was in the kitchen fixing dinner and the rest of the family was safe too. This hazardous tree story literally hit home for me because that little baby is my grandson.

I have talked often about not topping trees, but this story stresses why it is important to prune trees properly and to periodically assess large trees for the potential hazard that they may pose.
What qualifies a tree as “hazardous?” A tree is considered “hazardous” when all or part of the tree could “fail” and damage a “target,” such as a building, a vehicle, or people. Common failures are the breaking off of a tree limb, a tree splitting apart, or a tree uprooting and falling over.

There are a variety of reasons for failures including wood decay from past topping, other bad pruning cuts, or injuries to the bark and trunk; a lopsided crown; competing central leaders or main branches that are weakly attached at a less than 45 degree angle; the severing within the drip line of more than 50 per cent of a tree’s root system; and the development of significant girdling roots at the base of a tree.

The failure of a small tree is usually not significant, but the failure of a large tree can be catastrophic. When I first moved to this area in 1980 we didn’t have many large mature trees in our home landscapes, now there are many more. This is good, but it has also increased our potential for hazardous trees.

If you have a larger older tree, I urge you to check for any signs of potential failure in your shade trees and then consult an ISA certified arborist if you think there might be a problem. A certified ISA (International Society of Arboriculture) arborist can give you reliable advice regarding your tree and its health.

Signs of potential tree failure include:
– trees that have been topped in the past
– a tree that is leaning
– a tree with multiple trunks or with competing leaders
– trees with lopsided crowns
– trees with dead or broken branches
– trees with dead areas of trunk or signs of wood rot

If you have smaller tree that will grow into a big one, also consider having an arborist check it for any corrective pruning that is needed to avoid future problems. It is better and less expensive to take care of these problems when the tree is young.

It is possible that a consultation with an arborist prior to last week’s extraordinary wind event might have avoided the damage to my family’s home, the deaths of several people, and the property of many others, but there is no way to know for sure. Hindsight is always better than foresight.

Hiring an certified to take corrective action before a tree becomes a hazard is not inexpensive, but it is much less costly than having a tree come through the roof your house and potentially harming your family. A search of the yellow pages in the phone book or on-line will help you find a qualified ISA certified arborist. Please do this now before the next big windstorm.

Garden Tips, WSU Extension, Benton County, 5600-E West Canal Drive, Kennewick, WA 99336-1387, 509-735-3551, Contact Us

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