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Brittle trees paid highest price in storm

January 28, 2012

Willows, birches, poplars, cottonwoods and locusts: Their broken limbs and shattered trunks lay in heaps around Valley residences in disproportionate numbers following this week's ice storm.

It seems that the body-count bears out tree-expert predictions.

Some trees just aren't designed for rugged weather and those varieties top the list of "undesirables" most affected by our recent weather event.

"Willows are beautiful but they have a tendency to get rot and are really brittle," said Elizabeth Daniels, Oregon State University Master Gardener program assistant. "Some trees just aren't meant to live a long time."

Homeowners often plant fast-growing species like willows to reach shade-size height in a hurry. What they don't realize is the long-term cost that can be associated with those choices.

Fast-growing trees typically have more brittle wood and often develop large V-shaped diversions from their main trunks - creating inherent storm weaknesses in their structure. They also require more regular maintenance.

A "V" within a tree trunk is a place where water may collect or pool, leading to potential decay. Decay points are time bombs waiting to happen in a cold-weather event.

In addition, during ice storms, frozen water weight accumulates around every twig and branch, bringing incredible pressures on the weight-bearing infrastructure of the tree.

That is when tree design and cellular density really matter.

If you have a "sketchy" tree type in your yard, or have a "good" tree that hasn't been pruned in a while, you may already be a victim of this latest storm. However, it is not too late to learn about tree survival.

According to Daniels, "Using local orchards as an example, we can see that they sustained very little damage."

Orchards are regularly pruned and consist of locally appropriate trees. Older trees are also removed when they reach the end of their most productive time (a reflection of life expectancy).

"People who had been caring for their residential trees - having them pruned regularly - suffered much less damage," added Daniels.

Regular tree maintenance not only reduces surface area for heavy ice to adhere to, it also ensures owners can identify and remove rot-damaged limbs and keep dangerous limbs away from structures before there is a problem.

When it comes to storm cleanup for those trees with damage, pruning techniques are important - sometimes making the difference in the tree's long-term survival. See the sidebar illustration on step-by-step pruning techniques on A1. The Arbor Day foundation also provides an online video pruning tutorial at www.arborday.org/trees/pruning/.

With removal sometimes necessary, researching safe cutting and felling techniques or engaging local tree service companies will prevent potential injuries.

Choosing new plantings from a list of expert-suggested, climate-appropriate "street trees" is a good way to plan for the future. Those trees tend to be best-suited to handle differing growing conditions with the most stability, said Daniels.

On Jan. 25, OSU announced the release of the most sophisticated "plant-hardiness zone map" ever created in the U.S., created for the U.S. Department of Agriculture, providing a new tool for the estimated 80 million gardeners in the country who are seeking to plant appropriately for their climate.

The map was created by researchers at OSU using, for the first time, geographic information system (GIS)-based software that has resulted in an interactive map that is more accurate, detailed and useable than any previous model.

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