Outdoor Plant Care: Winterize Plants Outdoors

Many plants come through the ordeal in good condition, but others may be damaged unless we help them along. December is a good time to winterize plants that are newly planted, showing some pest or mechanical injury, or are otherwise known to be somewhat tender. Newly planted trees or trees that are known to have marginal hardiness should be given protection by wrapping the trunk. Wrapping is only necessary for a year or two on newly planted trees. However, tender types may need protection for many more years. Marginal plants should not be grown me except by the hobbyist who enjoys trying to grow plants that are a challenge and require extra attention.

The most common winter damage to tree trunks is known as sunscald. It occurs on the southwest side of the trunk when bark temperatures rises in the afternoon sunlight and drops sharply after sundown. This often causes the bark to split. In summer, insects or diseases may enter these splits, causing further trouble. On small trunks of thin branches the entire bark may be split off, causing the slum to be girdled and die.

Cold, drying winds are damaging to many plants, especially the broadleaved evergreens. Needled evergreens such as pine and juniper do not lose moisture as rapidly, but even these constantly lose moisture through their needles during the winter. This moisture must be replaced or the leaves will scorch at the tips or margins. Such damage is common on some hollies, rhododendrons and azaleas. Make sure soil around such plants is moist before it freezes. A heavy mulch placed over the soil helps retain moisture and prevents deep freezing of the soil. Wind screens also benefit tender plants, especially those planted during the past season.

Antidesicant sprays, often used to reduce drying in plant leaves after transplanting, can also be beneficial on evergreens during the winter. Such sprays form a film on leaf surfaces to help protect leaves from drying winds. Antidesicant materials are available from many nurseries and garden centers. Sprays should be applied December and again in early February for best protection. Some low-growing perennial flowering plants suffer more from freezing and thawing than from the cold itself. Such plants include chrysanthemum, delphinium and baby's breath. A loose mulch applied over them helps lo maintain the soil temperature at a more uniform level. Some of these plants develop green basal shoots in the fall. Since a heavy mulch would smother these basal shoots, a more open covering, such as evergreen branches, is better. Such a mulch shades them but still allows light and air movement around the small shoots.

Roses, such as the popular hydrid teas and floribundas also need winter protection. A mound of soil piled over the base of the plants 10 inches high gives good protection. Over the soil mound the additional protection of pine branches or inverted baskets may be placed. Tops of roses should be cut back slightly in the fall, but severe pruning should not be done until spring. Tender climbing roses should be pulled down to the ground and canes totally covered with either soil or a mulch. Tender berries, such as boysenberries, should also be treated this way.

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