Berks County Cooperative Extension -

PREVENTING WINTER INJURY

Ounce of prevention.

"Old Man Winter" sure can be brutal, but not just for humans. Many plant species can be very sensitive to cold temperatures and subsequent damage. Cold damage or winter injury can reveal itself in many ways. Have little fear because "an ounce of prevention is worth a pound of cure" when winter is upon us.

Frost injury.

Frost injury occurs when surface temperatures drop to 32ºF or lower. This is the most common type of cold damage. Frost most commonly damages tender annuals, but can also damage flowers and young fruits on trees and other landscape plants. This damage occurs most frequently in the early spring.

Frost injury can be prevented by keeping buds from opening up too soon. For example, plant magnolias on the east or north side of a building so early sunshine won't fool them into an early spring. Selecting late flowering cultivars is also an option.

Soil heaving.

Soil heaving is caused by alternate freezing and thawing of the soil due to temperature fluctuations. This heaving can push shallow plant roots up out of the soil, leaving them exposed to cold and desiccation (drying out completely). This affects new and shallow-rooted plants the most.

Soil heaving can be prevented by applying a two- to four-inch layer of winter mulch (after the soil has frozen). Applying mulch at this time provides insulation and maintains a constant temperature. Remember to keep mulch pulled back from the crowns of perennials that are susceptible to rot.

Freezing injury.

Freezing injury occurs when the cell membranes are fractured and disrupted. Freezing injury damages plants in the dormant state (as opposed to frost injury). Tender buds of flowering trees are usually affected, as well as trees and shrubs housed in containers.

Freezing injury can be prevented by planting the plant in a protected spot and insulating it. Movable containers can also be placed in a protected area, buried in the ground, and mulched.

Freeze cracks.

Freeze cracks occur when there is a sudden change in temperature causing the bark of some trees to split. Thin-barked trees like maples, poplars, sycamores, and cherries are most susceptible to this injury.

Freeze cracks can be prevented by shielding the tree trunk from direct sun, although many young trees have the ability to heal freeze cracks on their own.

Winter burn.

Winter burn occurs when evergreens become desiccated. Evergreens continue to lose water through their leaves in the winter. Windy conditions and sunny days will speed this process.

Winter burn can be prevented by keeping evergreens well watered as they enter the winter season. Adding mulch can conserve soil moisture. Remember to water plants when soil thaws during the winter.

Cold-hardy plants.

Understanding winter injury and how to prevent it can allow gardeners to maintain a healthy landscape. Choosing cold-hardy plants is the first and most important step in protecting plants from cold damage.

Author: Laura L. McNutt, Extension Agent - Horticulture
Document created: 4 February 2001