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Environmental Horticulture (Gardening)

Winterizing Trees and Shrubs

By safeguarding your established trees and shrubs for winter, you help minimize the damage caused by surface run-off and erosion and subsequent water pollution.

It is often necessary to give a little extra attention to plants in the fall to help them make it through winter and start spring in peak condition. Utilize cultural practices that will help you reduce winter damage of ornamentals.

Select hardy plants. Grow plant materials that are native or are known to be winter-hardy in your area.

Select an appropriate site. Some varieties of rhododendron, azalea, camellia, daphne, and holly need a location on the north, northeast, or eastern side of a building or other barrier where they will be protected from prevailing winds and intense winter sun.

Avoid poorly drained soil, low spots that create frost pockets, and sites that are likely to experience rapid fluctuations in temperature.

Practice late fall fertilization. Fertilize after plants are dormant but before soil temperature drops below 45o F. to help prevent winter damage. Avoid late summer or early fall fertilization while plants are still active, as this stimulates late fall growth which is easily killed by freezing.

Prune at the right times. Proper pruning at appropriate times throughout the year is effective in reducing damage by ice and snow. Avoid late summer pruning, which stimulates new, tender growth and reduces the supply of nutrients available to the plant through the winter.

Be sure your plants have enough water. Proper watering can be a critical factor in winterizing. If autumn rains have been insufficient, give plants a deep soaking that will supply water to the entire root system before the ground freezes. This practice is especially important for evergreens. Watering during January, February, and March, when there are warm days, is also important.

Mulch to control erosion, soil temperature, and loss of water. A 2-inch layer of mulch material such as fir bark, pine needles, or wood chips will reduce water loss and help maintain uniform soil moisture around roots. Mulching also reduces freezing and thawing of the soil which heaves some shallow-rooted plants, causing significant winter damage.

Remove snow that is collecting on branches with a broom. Always sweep upward with the broom to lift snow off. When the branches are frozen and brittle, avoid disturbing them. Wait until a warmer day.

Protect newly planted trees. Bark splitting, especially dangerous on young trees, is caused by the extreme fluctuations in temperature. The afternoon sun on exposed trunks raises the temperature much higher than the air and the sudden drop at dark causes splits and cracks. It can be prevented by wrapping trunks with burlap strips or a commercial tree wrap or shading the southwest side.