Do I need to apply a winter mulch to my landscape plants?
To reduce the effect of alternate frost heaving and thawing, apply a winter mulch after the soil freezes. When mulch is applied to frozen soil it will keep the soil consistently cold. Mulch will also help to retain soil moisture. The mulch layer should be 2 to 2 ½ inches thick and can be composed of leaf compost, straw or other material.
Courtesy of the NYBG Plant Information Service