Snow-felled trees are wake-up call

Over the past several weeks, tree branches, and in many cases, entire trees have been felled by heavy snow.

Removal and replacement costs could climb into the millions of dollars. Throw in the additional cost of property damage and the safety concerns of downed power lines, and the situation is a wake-up call for better tree selection and care.

While driving around the northern part of the state over the past couple of weeks, I noticed that the fast-growing trees created the most serious problems. In the arboriculture world, fast growth is synonymous with inherent weakness. Trees that grow quickly are never as structurally sound as slow-growing trees.

Fast-growing trees generally have weak wood and often develop a poor branch structure. In particular, Siberian elms suffered many injuries and created many problems. In addition to having weak wood, these trees have another inherent weakness — their natural shape, an upright inverted cone, collects snow that falls over a wide area.

As the trees collect the heavy, wet snow on the uppermost branches, the laws of physics take over. The weight of the snow and the long, brittle branches create a huge strain on the trunks. Since all of the branches form narrow crotch angles and connect at one point, the branches split off the trunk, and in many cases, the entire tree splits apart.

Globe willows, cottonwoods and poplars share the same inherent weakness. Because of their extreme tendency to break apart, these trees should never be planted near buildings or power lines.

The quaking aspen and Lombardy poplars have weak wood but show fewer problems because of their narrow, upright shape.

Bradford pears and flowering plums suffered extensive damage from the recent storms, because they have many branches coming out from the same point on the trunk. Newer cultivars of the flowering pears show fewer problems because they have a stronger branch structure.

So what are the better choices to plant? Structurally, look for trees that have branches that are spread along trunk instead of all coming out in the same place.

Correctly pruned or trained maples and London plane trees are not as likely to show damage. Other deciduous trees that are more likley to survive such a storm include oak, gingko, honey locust and beech.

Coniferous trees, such as pines, firs and spruces have a narrow, pyramidal shape, and relatively short, flexible branches. These usually are resistant to snow damage.

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Larry A. Sagers is the regional horticulturist, Utah State University Extension Services, at Thanksgiving Point.