City arborist offers advice to protect trees for winter

November 29, 2011

By Tom Corrigan

Issaquah city arborist and horticulturalist Alan Haywood said trees can suffer significant damage in winds of about 40 mph.

And Haywood said winds of that strength are not all that unusual in Issaquah. So, what do you do about the potential problem?

“Well, you can’t do anything to stop the wind,” Haywood said.

But there are steps you can take to protect both your trees and your home and other property from damage. Kevin Zobrist is a forestry educator for WSU and was one of the instructors for a recent outreach course on protecting trees. He said unhealthy or potentially hazardous trees will exhibit several warning signs, including yellowing or thinning foliage. Zobrist said the most common tree problem locally is root rot, a type of fungal infection.

According to Zobrist, the Douglas firs common in the Northwest are particularly susceptible to root rot. Some signs include a rounded, as opposed to a pointed, treetop.

Regarding potential wind damage, there are numerous steps that can be taken to protect trees and there are steps that should not be taken, Zobrist said. He opposes what is often called “topping” trees, the removal of upper foliage and limbs presumably to make the tree less prone to wind damage.

“That’s fine if you’re trying to kill the tree,” Zobrist said, adding that is a “strong statement,” one with which some tree experts might not agree.

Haywood said most trees under stress fail at identifiable weak points, which may or may not take a professional to identify. He said in most cases, once a weak point is identified the tree owner needs to think about pruning, or in extreme cases, removal of the tree.

What do you do when a tree becomes damaged?

“In a best case scenario, just some pruning will be needed,” Haywood said, though he added the necessary pruning could be significant.

Zobrist said downed trees or branches need to be removed or protected from insect infestation that can spread to healthy trees.

The city of Issaquah regularly inspects trees on public property, on landscaped streets such as Gilman Boulevard and at least on the fringes of green or wild areas. Haywood said the city is not responsible for trees on private property. If it turns out a tree on private property needs to be removed, Haywood noted the city has various rules regarding the removal of trees.

For example, any tree more than 30 inches in diameter is considered a landmark tree and is protected. Trees on steep slopes are often protected as well since their roots help keep those slopes in place. There also are rules spelling out how many trees a property owner can remove. There are exceptions made if trees prove to be overly hazardous.

For trees on public property or in right of ways, Haywood said the city often depends on private citizens to let officials know if a tree is a hazard or potential hazard. If you notice something you don’t like about a tree on public property, Haywood urged residents to call either the Parks & Recreation or Public Works Operations departments.

Tom Corrigan: 392-6434, ext. 241, or Comment at

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