When checking your fall to-do list, be sure anti-desiccant is on it. This wax-like spray-on material is the most economical, effective protection for winter vulnerable evergreens.
If you’re not familiar with anti-desiccant and the way it protects your evergreen trees and shrubs, here’s a quick introduction. Deciduous trees and shrubs (those that drop their leaves in winter) go dormant but evergreens (both broadleaf and needled) simply slow down their life functions. This means the leaves continue to produce food through photosynthesis all winter long.
In the process of photosynthesis, plant roots absorb water and nutrients from the soil and transport them to the leaves or needles. The leaves/needles also absorb carbon dioxide (CO2), much of which we exhale when we breathe. In a complex reaction with the sun and green chlorophyll in the leaves/needles, water and CO2 are converted to sugar (glucose) that feeds the plant.
Water and oxygen (which we breathe), the waste product of photosynthesis, are given off through the leaves/needles in a process called transpiration.. In the winter, however, the ground is frozen so the roots can’t absorb water. Instead, the leaves/needles, reabsorb the transpired water and recycle it. The problem is that winter winds can blow the water droplets off the leaves before it can be reabsorbed. Anti-desiccant forms a protective barrier that reduces the chance of transpired water being blown from leaves and needles.
As temperatures rise in the spring, they thaw the frozen soil so roots can again absorb water. At the same time, the warm sun melts the anti-desiccant so the leaves/needles can again transpire water normally. If we have an especially mild winter, the warm sun may melt the anti-desiccant prematurely, in which case you’ll need a second application.
Several brands of anti-desiccant are sold in spay bottles at garden centers. The best known brand is Wilt-Pruf. Applying anti-desiccant to one or two evergreen shrubs is easy. If you have a number of evergreen trees and shrubs, however, applying it yourself can be exhausting, especially for the hand you are using to pump the sprayer. Buying a number of small spay bottles can also get expensive. In that case, it’s easier and more economical to have one of our Plant Health Care professionals apply it using a powerful backpack sprayer that can reach even the treetops.
Anti-desiccant’s one restriction is that, regardless of whether you are applying it yourself or professionally, it has to be applied before temperature drops below freezing.
Even though I used anti-dessicant only once, I do not miss it. We applied it to the cultivars of citrus that were more sensitive to frost. We were not so concerned about major damage, but wanted to preserve their healthy green sheen through an unusually cool frost. Humidity is minimal here, particularly during frost. (Mexican lime defoliates anyway, so there is no foliage to preserve.) To me, it was like lacquering polished silver. It works, but just seems wrong. In the end, the foliage looked great though.