Last winter's very cold weather caused major damage to ornamental landscape plants. Gardeners asking what they can do to help their plants survive if this winter is as bad as the last one.
Three different kinds of winter-injury can occur to trees and shrubs.
One kind is extreme cold. Each variety has its own degree of cold hardiness that depends on its genetic makeup. One variety may be hurt if the temperature goes much below freezing while another may be able to survive minus-20 degrees when fully hardened (cold acclimated).
The best way to prevent damage from extreme cold is to use plants that will not be damaged by low temperature.
Heavy mulching (five or six inches) with tree bark or something similar, a wind break to protect the plant from chilling winds, and shade will often bring a plant through that otherwise might have been lost.
Another winter injury is due to desiccation. If the soil is frozen deep and all the roots are in frozen soil, the roots cannot supply moisture to replace that lost by the top of the plant. Browning and death of evergreen foliage may occur. The longer the freezing spell, the greater the injury they may experience.
Two things may be done to help in this situation. One is to shelter the plants from sun and wind to reduce moisture loss by the foliage. The other is to use a heavy mulch to reduce the depth of freezing.
The third kind of winter injury is caused by failure of plants to harden in time for winter weather, or to break dormancy to mid-to-late winter when mild weather occurs and is followed by severe cold.
Bark splitting on young newly planted shade trees can be prevented by wrapping the trunks with treated papper or burlap, according to Dr. Frances R. Gouin, University of Maryland horticulturist.
To accomplish the same effective control without taking a great deal of time, paint the stems and lower branches with the cheapest white latex paint you can buy, Gouin says. The white paint reflects the light and minimizes rapid temperature fluctuations known to be responsible known to be responsible for much of the bark splitting that occurs in the East.
Antidesiccants, such as Vapor-Gard and WiltPruf may help in protecting evergreens from excessive drying. However, they offer little or protection against deep freeze injury.