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Inconsistent weather has been damaging to trees

Published: Sunday, Jan. 29 2012 5:58 p.m. MST

Broken Siberian elm trees on the University of Utah campus couldn't withstand the recent snowstorms.

Larry Sagers

Trees are having a tough year! Some were hit with some difficult diseases because of the cool, wet spring and early summer last year. The usual plethora of insects and summer problems made the plants suffer even worse.

The tall, upright conifers in Davis and Weber counties had a tough time withstanding the onslaught of the severe winds. Many thousands crashed to the ground, taxing the resources of cities, commercial arborists and even the disposal sites.

The unseasonably warm December had many trees acting like it was spring. Large, swollen buds on poplars, cottonwoods, willows and others had many people wondering what was going to happen when winter finally came.

Although the snow was late in coming and intermittent, it, too, has caused considerable damage. Split trunks, broken branches, distorted terminals and leaders are all signs of excessive damage from snowfall.

Successful tree plantings always start by putting the right plant in the right place. Often, poor plant choices lead to high maintenance, increased costs, excessive storm damage and even personal injury or even worse.

With that in mind, look for trees that will withstand potential damage. Avoid what are commonly weak-wooded trees. Trees are considered weak for two different reasons.

The first reason why the trees are considered weak is that they a have soft, lightweight wood. Because these trees grow very quickly, the cells are very large. That leaves a lot of airspace between the cell walls so the trees are very prone to break down.

The second reason why trees are weak is the structure of the tree. Most trees that develop narrow branch or crotch angles do not knit or grow together. Instead of having branches that are tightly knit together, the branch angles are filled with dead bark, old leaves and an assortment of dirt and dead insect bodies.

Trees with weak wood include all members of the Poplar genus. Aspens of all kinds and all the species of cottonwoods are included in this group. Willows are another group of trees that are extremely weak-wooded.

The Tree-of-Heaven is another weak-wooded tree. The smaller branches have more soft pith than woody material, so they break very easily. The larger trees have a very poor branch structure and break down easily.

Box elder maple is another tree with soft wood. It produces extensive rapid shoot growth so the shoots break down under stress. The silver maple also has serious problems with structural weaknesses.

Some willows have both weak wood and poor structure. Among the worst offenders are globe willows. These trees have all of the branches arising from one point on the trunk. That means with stress or pressure on the tree, it is likely to split the tree down the middle and destroy it.

Other trees with very poor structure include the Siberian elm. This tree has become a difficult tree to manage because the branches grow at very narrow angles. When the tree becomes weighted down with snow or is exposed to strong winds, the branches fail.

Branches on conifer trees are usually flexible enough and structurally placed so that they do not break down easily, but they still have problems. Spruces have very shallow root systems and as they grow, they become very top-heavy and very prone to tip over in the wind.

Arborvitae trees also have their share of problems. The biggest problem in our area is snow. The trees tend to have all of the foliage on the outside perimeter of the tree, and when snow catches that foliage, it pulls the tree apart and exposes the dead foliage on the inside.

While there is no such thing as a perfect tree, you can greatly reduce damage from tree breakage by selecting better trees for your landscape. Don't overlook the other growth factors, because these also contribute to the desirability of a tree.

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