Tree care important for safety.

Byline: SCOTT MABEN The Register-Guard

They tower over us and shield us from the elements, but trees aren't as invincible as they look.

In urban areas especially, the oak, the maple, the fir and other varieties are routinely sabotaged by development, ill-advised landscaping, reckless maintenance and other detrimental deeds, arborists point out.

Poor tree care was a key factor in the loss of thousands of trees in the brief but powerful windstorm that sliced through the southern Willamette Valley last February.

Aiming to limit such storm damage, forestry officials will co-sponsor a series of seminars next month on how to keep trees from becoming hazards. The day-long sessions in Albany, Roseburg and Coos Bay are aimed at landscapers, utility workers, highway maintenance crews and others who work around trees.

"A lot of people have misconceptions about trees," said Paul Ries, urban and community forester for the state Department of Forestry. "They don't know how close they can get with the mower, they don't know how much they should water, they don't know how many roots they can sever."

Human influences can determine whether some trees withstand strong winds while others "snap like matchsticks," he said. More than 1,000 trees in the Eugene area alone fell or were uprooted during the Feb. 7, 2002, cyclone that wreaked havoc across Coos, Curry, Douglas, Linn, Lane and Benton counties. Scores fell on homes, cars and powerlines.

Seminar organizers don't want that to happen again and are attempting to get the word out about tree care.

"This seeks to target that population of people who don't necessarily think about trees that surround them every day and how dangerous they can be if they become hazard trees," said Patty Williams, executive director of the Pacific Northwest Chapter of the International Society of Arboriculture, which is sponsoring the seminars with the Department of Forestry.

"People do not necessarily know what hazard trees look like," Williams said.

A tree usually becomes a hazard when its roots are damaged, compromising the stability of the tree or depriving it of water and oxygen, Ries said.

"We want to help them understand that the actions they take can actually affect the future health of trees, whether it's digging a trench or mowing the grass," he said.

Common myths about trees are that they have deep tap roots and root systems that extend only as far as the drip line - the edge of the tree's canopy. Older trees generally have no tap root, Ries said, and their roots spread beyond the drip line. The vast majority of the root system is shallow, located in the first couple feet of soil.

"Imagine a wine goblet perched on a pancake: That's a good representation of what a tree looks like," Ries said.

Paving over roots for streets and sidewalks and severing them when digging trenches for sprinkler systems or utility lines weaken trees and puts them at risk of decay and disease, experts say.

Trees also suffer if additional soil or mulch is piled around their trunks or on their root systems.

Routine lawn maintenance is a common culprit in creating hazard trees. Mowers that scrape trunks and weeders that nick younger trees with thin bark introduce decay and may even kill a tree.

Overwatering also can spell disaster for trees that are adapted to dry summer conditions. Regular summer watering may keep the lawn green, but it also keeps the root systems of trees wet and susceptible to rot, Ries said.

Last February's storm claimed many white oaks in lawns that had been overwatered, he said.

"They were made easy targets for the storm to pop them over," he said. "Many people don't realize when they water their lawn, they're also watering their tree and causing the decline of that tree."

Douglas firs were the predominant victims of the storm in Eugene, partly because they were saturated with water and their branches caught more wind than bare leaf trees, said Mark Snyder, urban forester for the city of Eugene.

Every felled fir that Snyder saw had root rot. It likely developed from a combination of mechanical damage - construction, landscaping, irrigation installation - and summer watering, he said.

The city each year removes about 150 to 200 hazard trees, mostly along streets. Through several city programs, more than 1,000 trees are planted each year to replace trees that have been removed or to landscape new developments.

The hazard trees seminar is funded in part by a $15,000 grant from the Federal Emergency Management Agency in response to last year's windstorm. The materials will be posted on the Internet - www.pnwisa.org - for homeowners and others who work around trees.

Property owners seem more interested in the health of their trees since the February storm, said Eugene arborist Harry Leuallen.

"I've gotten a lot of calls from people worried about their trees for one reason or another," Leuallen said. "But a lot of people are ignorant about what things in trees are hazardous. They will call and they have no idea if their tree is hazardous or not."

Some of the signs that a tree may be in trouble include open cracks in the crotches between limbs or stems; decay on the trunk or large limbs; raised ground around the trunk; excessive weight on the ends of branches from poor pruning; and mechanical injuries.

Another big mistake people make is to top a tree - literally lop off its top - in hopes of controlling the growth, Leuallen said.

"It's not always fatal, but it certainly causes a tree that could have been pruned and made nice to become a total aberration, with the potential to be unsafe," he said.

The Eugene Water & Electric Board used to top trees under power lines but stopped the practice around 1990, spokesman Marty Douglass said.

"Now we do directional pruning, and we try to be as least invasive on the tree as possible," Douglass said.

HAZARD TREES SEMINARS

Albany: Feb. 4, Linn Benton Community College.

Roseburg: Feb. 11, Umpqua Community College 

Coos Bay: Feb. 12, Southwestern Oregon Community College 

Cost: $20

Registration: www.pnwisa.org/ news.html

Information: [phone]

- Oregon Department of Forestry

AVOIDING HAZARD TREES

Common mistakes that create hazard trees:

Overwatering: Heavy summer watering can cause root rot in native trees. Avoid watering more than once a week, and aim sprinklers away from root systems.

Cutting roots: Avoid severing roots for ditches, landscaping and construction.

Covering roots: Do not spread soil or mulch on top of root systems, and don't pile any up against the trunk, where fungus may grow. Do not pave over root systems; it will deprive the tree of water and oxygen.

Mechanical injuries: Scraping the bark can damage and even kill a tree. Be careful with lawnmowers, trimmers and weeders.

Cavities: Don't clean out cavities or pockets, and do not fill them with cement. This is the tree's way of sealing off a wound. Leave them alone.

Topping: Don't attempt to halt growth by topping a tree. It will grow abnormally.

Information: To learn more about proper tree care, visit the International Society of Arboriculture's Web site at www.isa-arbor.com.

- Oregon Department of Forestry, Pacific Northwest Chapter of the International Society of Arboriculture, City of Eugene urban forester