Trimming won't spare trees from the heavy snow

When tree limbs snap and power lines fall in bad weather, is it the result of Mother Nature's vengeance or payback for neglectful homeowners?

Edina and Minnetonka, with thousands of mature trees, were hit hard two weeks ago when 10 inches of sloppy snow fell. Both cities were still cleaning up storm damage over the past week.

At an Edina City Council meeting last week, officials noted that the city had been especially plagued by power outages. One council member wondered whether homeowners could do anything to help prevent such problems, saying a resident had called her to suggest that perhaps people were not trimming their trees appropriately.

Xcel Energy executive Fletcher Johnson called most of the damage from snow on Nov. 13 and during high winds on Oct. 26 "nonpreventable."

Johnson oversees Xcel's "vegetation management" in Minnesota, the Dakotas, Michigan and Wisconsin. He said much of the damage from the pre-Halloween low pressure system was from tall evergreens that were uprooted by wind gusts up to 65 miles per hour. Those trees are usually not pruned.

"A fairly large percentage [of power outages] were caused by evergreens and spruce trees that literally just blew over and snapped apart," Johnson said. "Those were the trees that were catching the wind."

The damage would have been even greater if most deciduous trees hadn't already dropped their leaves, he said.

Johnson said trees are "designed to bend," but this snow was so heavy that many trees bent until they broke or fell over. He estimated that at least 80 percent of toppled trees and broken branches could not have been predicted to fail.

Edina City Forester Tom Horwath said that after the storm he saw many trees that had shed dead wood under the snow's weight, but he also noticed fallen trees with weak points that would have been invisible from the ground.

"Once they came down you could see obvious points ... that were structurally weak, rotten wood or cavities in the wood," he said.

Horwath said he believes Edina residents care deeply about trees and said many are diligent about pruning and tree maintenance. However, he said trained arborists who work in tree canopies may be able to spot branches that are in danger of eventually failing.

"Good tree trimmers know which branches are likely to fall if left on a tree," he said. "Tree trimming is better a little bit at a time but more often, especially when trees are young."

Like Edina, Minnetonka removes any branches or debris blocking roads and sidewalks, and trims hanging and damaged branches over public right-of-ways. But anything deeper than 6 feet into a lot from the curb is residents' responsibility.

Colleran, a trained arborist, said she didn't think neglect had much to do with tree damage in her city.

"The trees that I looked at, the limbs that broke were not structurally unsound," she said. "Most of it was caused by the weight of the snow that had fallen, not because people were not taking care of their trees."

Minnetonka tries to educate residents about tree care, with an annual tree sale and clinics on tree planting and care. The city's Web page has a guide to picking tree trimmers, with a list of firms that have given the city proof of liability insurance. Companies with licensed arborists on staff are starred.

Xcel has the right to prune trees that are growing near power lines even if they are on private property. Johnson said private tree trimmers hired by Xcel cycle through neighborhoods every four to five years to prune branches away from pole-to-pole power lines.

"Sometimes trees don't look the most aesthetic when we're done, but they are pruned to a nationally acceptable standard to keep trees as healthy as possible while keeping the power supply safe," he said.

But at Edina's City Council meeting, City Manager Scott Neal noted that Xcel's aggressive pruning may give residents incentive to hire their own arborists.

"It's almost always a better idea for residents to do it," he said. "They almost never appreciate how Xcel does it."