Evergreen plants, both narrow and broadleaf, continue to lose moisture through their leaves in winter. If the soil is frozen, ground moisture is not available to plant roots and they cannot absorb what is lost through the leaves. The foliage becomes dry and brown and may drop. Applying anti-desiccant coats the leaves and reduces transpiration. Usually two applications per season are necessary for protection, one in December and the other in February. Wrapping evergreens with burlap or canvas is also helpful to reduce desiccation from sun and wind. Leave the top of the wrapping open to allow sunlight to penetrate.

Courtesy of the NYBG Plant Information Service