If you have evergreens in your landscape, anti desiccant is their best protection against winter burn. Regardless of whether they’re broadleaf evergreens like boxwoods and rhododendrons or coniferous like pines and junipers, I strongly recommend this effective, economical, easy to apply protection. It’s also why I issue this reminder every fall.
Winter burn can occur when the leaf or needle surfaces are deprived of water. Unlike deciduous trees that go dormant for the winter, evergreens’ metabolism simply slows down. The green leaves or needles are still making food through the energy trapping process of photosynthesis.
Water is an important part of the photosynthetic process. It’s normally absorbed by the roots and carries nutrients to the leaves by way of the plant’s xylem. Water, also a byproduct of the process, is given off through the leaves. This is called transpiration.
When the ground’s frozen and the roots can’t absorb water, the plant reabsorbs transpired water and recycles it during photosynthesis. While on the leaves, transpired water picks up nutrients from the air, similar to the way those curious air plants in the genus Tillandsia get their water and nutrients.
This is fine until the wind blows. Wind picks up transpired water droplets and carries them away before they can be reabsorbed. When this occurs, photosynthesis shuts down and the affected leaves, needles and branches dry out and die. Desiccation is defined as dehydration, withering, shriveling and drying.
Desiccated leaves and branches turn brown but the whole plant rarely dies. It just has ugly brown patches, and the only remedy is to cut out the dead wood. This affects the aesthetics of an otherwise graceful, beautiful evergreen.
Anti desiccant is a wax like material that’s sprayed on the leaves or needles to trap transpired water until it’s reabsorbed. Anti desiccant’s consistency is such that its application is very weather dependent. It can freeze when it’s cold and melt when it’s warm. Applications are made on days when the temperature is below 50ºF and above 32ºF (freezing). If we get sustained warm spells, as we did last winter, additional applications may be necessary. Nothing has to be done in spring, though. The anti desiccant just melts when the weather warms up.
Garden centers and home stores sell anti desiccant in spray bottles. The most familiar brand is Wilt Pruf, and it’s in easily recognized green bottles. Buying one or two of these bottles to apply to a couple of evergreen shrubs is a good DIY project. Any more and your hand will let you know how hard it is to squeeze those spray triggers.
For properties with many or large evergreens like towering conifer trees, it’s more economical and efficient for one of our Plant Health Care professionals to apply anti desiccant. We buy it in bulk, which is considerably less than buying those consumer-size containers at retail, and you don’t have to worry about properly disposing of the empty containers. Our PHC pros apply anti desiccant with backpack sprayers that have enough pressure to reach the tops of tall trees.
Before anti desiccant, it was common to wrap all evergreens in burlap. Today, only plants affected by salty road spray, young trees and shrubs that are still getting established, or tender plants that may be near the limit of their hardiness zone benefit from wrapping. The others are sufficiently protected by anti desiccant.