Regional Gardening Reports :: National Gardening Association

In the Garden:
Western Mountains and High Plains
November, 2009
Regional Report

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Don't be in a hurry to knock snow off trees and shrubs. Most are equipped to cope.

Ready Trees and Shrubs for Winter

The trees and shrubs in your landscape have built-in coping skills to help them survive during the winter. Deciduous trees and shrubs drop their leaves, store energy reserves, and go dormant over the winter. Evergreens, however, take a different path. They endure the colder temperatures by slowing down growth -- but not going dormant -- until spring returns.

Even though plants have these natural defenses, it is a good idea to help them get ready for the upcoming winter in every way you can, especially plants that aren't native to the region. Gardening is a year-round partnership that often requires your intervention.

One of the first things to do to ready borderline-hardy plants is to encourage strong growth and development during the growing season and beyond. Perhaps most important is to give them a deep late-fall watering if weather permits, before the ground freezes. Give them a slow, deep soaking that will allow the water to get down deep around the entire root system.

With the fickle weather throughout the region, there are constant challenges that trees and shrubs face as temperatures plummet and then rebound for extended periods. Lots of snow can fall quickly, but then melt in a day or so. This is where you can lend a helping hand when conditions warrant your intervention.

Heavy Snow Loads
It is not unusual for a snowstorm to hit the region and with heavy snowfall and big accumulations. Snow will build up on the branches and foliage of evergreens. The stress from this weight can deform the weaker branches or even snap them off. But trying to remove the snow and ice at the wrong time can do the plant more harm than good.

Don't try to knock a heavy load of snow from frozen branches with brooms or rakes. The impact can cause the branches to snap off. If the branches are bending badly, it is much wiser to support them temporarily by using two-by-fours or other lumber under the outer ends. Then, as the weather warms and the snow melts, gently shake the branch by hand if snow doesn't fall off on its own.
Some trees are naturally equipped to tolerate heavy snow loads. My littleleaf linden is very durable, as are the oak species, ginkgo, Douglas fir, spruce, arborvitae, spireas, viburnums, and lilacs.

Although, it is hard to leave laden branches alone, don't do anything for shrubs and trees covered with ice. Removing ice from large limbs is futile and will easily shatter the branches under the weight of the ice. Limbs will come crashing down onto you or other objects.

To help trees and shrubs endure during the snow, it is important to prune out thinner, weaker branches and poorly developed branch attachments. Narrow angled branches attached to the trunk are the most vulnerable. Keep limbs and branches with wider crotch angles as they are stronger and able to bear more weight.

The damage referred to as sunscald is most common on young, thin-barked trees. It starts on winter days when the bark will warm up and cells become active. Then, when the temperature plummets at night, freeze or desiccation will start and the bark will expand and split. Older trees are generally not affected because they have already developed thick bark which reduces rapid heating of the cells.

You can prevent sunscald on susceptible trees by wrapping the trunks with a commercial tree wrap that will help reflect the sun on the south and west exposures. These are intended to keep the bark temperature more constant. My recommendation is to start tree wrapping around the Thanksgiving holiday, and mark the calendar to remove the wrap around Easter in the spring. This will allow the bark to develop normally during the growing season and toughen the tree's resistance to future problems.

Newly planted trees should be wrapped for the first two winters. Then, they can be on their own. Some of the more susceptible trees should be monitored yearly and, depending upon exposure, you can determine if they need additional protection.

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