Holmberg speaks with master arborist about assessing tree risk

Posted at 11:59 PM, Jul 02, 2012
and last updated 2012-07-02 23:59:52-04

RICHMOND, Va. (WTVR)--Trees are like people. Each one is different.

And how and where it grows up can determine the likelihood of it falling – or weathering the storm.

“The three things that determine risk in trees is the tree itself, the environmental situation that the tree stands in, and the presence of a target,” explained Janine Lester, a master arborist with Landscape Design Consulting in central Virginia.

A target being a house, car, power line, “playground, school, any kind of manmade structure or foot traffic likelihood,” Lester added.

“Certain species do show an increased likelihood for breakage in storms, they are weak-wooded by nature,” she said, naming silver maples for one. Some species, like oaks, tend to hold up very well in storms.

Trees with “co-dominant trunks” – those with a trunk that splits into two near the stump, are riskier because they can be whipped around and sort of fight against each other.

The location, the environment of the tree, is also critical. A tree-standing alone, or in a spot where the wind is channeled can add to its possible peril.  Just parking or driving beneath its drip line – usually the span of its roots -can compromise it. So can banging into it, or even just a clothesline.

It’s very difficult to see what kind of stresses the roots have faced during its lifetime, which is one of the reasons why predicting the storm-resistance of a tree is an imperfect science.  Lester said three qualified arborists could examine that same tree and come to three different conclusions, “all of them defensible.”

Lester said there are some common misconceptions, such as wet soil contributes to tree falls.

Also, she said, just because a tree is partially hollow or has some areas of decay doesn’t necessarily mean it’s a menace.

And even the healthiest tree can be snapped off or ripped from the ground by a wind that hits it hard enough, in the right direction.

You can find a qualified local analyst to check your trees at the  International Society of Aboriculture website:

Your local agriculture agent or Department of Forestry representative can also give you some advice.

Trees add tremendous value to a property, and to a municipality, well beyond their beauty. They help cool in the summer and cushion winter winds. They clean our dirty air, sheltering a host of animals most of us enjoy.

But remember, like humans, all trees eventually fall to the winds of life.