Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: THURSDAY, October 26, 1995                   TAG: 9510260003
SECTION: CURRENT                    PAGE: NRV-8   EDITION: NEW RIVER VALLEY 
SOURCE: JOE HUNNINGS
DATELINE:                                 LENGTH: Medium

AVOIDING WINTER PLANT DAMAGE

The majority of winter damage can be divided into three categories: desiccation, freezing and breakage. Desiccation, or drying out, can be particularly damaging to evergreens, causing discolored or burned foliage and even plant death. Leaves continue to transpire in the winter, though at a lesser rate than in the summer. Winter winds can increase the rate of transpiration, causing the plant to dry out, particularly if the ground is frozen and the plant cannot take up more water.

Freezing damage most commonly occurs in the fall or spring, when green wood (new growth) or blossoms are susceptible to sudden frost. Mid-winter freezing often takes the form of bark splitting. On a relatively warm day, the sun can really heat up dark-colored tree trunks and get the sap flowing. A severe freeze that night can cause the bark to split.

Breakage is usually caused by a combination of ice, snow or wind. The weight of ice and snow can break even large, strong branches, especially if the wind further taxes the plant's physical strength. Improper removal of ice and snow can cause breakage. Frozen, laden limbs are very brittle and snap easily if bent the wrong way.

Plants damaged by harsh winter conditions can be avoided by planning ahead. Select hardy plants. Grow plant materials that are either native or are known to be winter hardy in your area. Select an appropriate site for more tender specimens - well- drained, out of winter wind and sun (north, northeast, east sides of house), and away from eaves where falling snow may break branches.

Avoid late-summer or early fall fertilization that may stimulate new growth for frost to kill. Fertilize in late fall when the plants can use the nutrients to keep their strength, rather than put on new growth. Avoid late-summer pruning, as this also stimulates new growth, but keep the plants properly pruned at appropriate times to remove weak branches with narrow crotch angles. Water plants deeply in preparation for winter, especially if there has been a dry autumn, and especially soak evergreen plants. Also, water deeply on warm days in January, February and March.

Mulching reduces water loss and soil heaving while allowing the roots a little more time to grow in the fall. Leave several inches of bare ground between the trunk and the mulch to discourage mice from nesting and feeding on the bark.

Remove snow before it can accumulate by sweeping the branches upward with a broom to lift off the snow without further stressing the limbs.

Shade trunks of young trees with a board or wrap in cloth or paper to reduce the chance of bark splitting. Bark splitting is caused when dormant trees are coaxed into cambial activity on warm winter days, especially when trees are exposed to direct sunlight. When freezing temperatures return, the active cambial tissue is killed, causing the frozen bark to separate from the wood of the trunk. Shading the trunk prevents the bark from heating up, thus preventing bark from splitting.

Joe Hunnings is the Virginia Cooperative Extension agent for agriculture in the Montgomery County Extension Office in Christiansburg. If you have questions, call him at 382-5790.