Sure, your evergreens stay beautifully green through the winter. But have you noticed them turning brown come spring? Oftentimes, browning and curling of evergreen foliage in the spring is the result of desiccation (moisture loss) occurring over the winter season.
Cold weather means frozen ground, and that means less moisture making its way to the roots of trees and shrubs. At the same time, moisture is escaping those trees and shrubs through their foliage (via stomata located on the underside of leaves and needles). This moisture loss is characteristic year-round, but (a) during the winter, there may not be enough water in the soil to replenish what’s lost through leaves and (b) dry winter winds are especially prone to dehydrate foliage.
Deciduous trees know their limits. Their wide, relatively fragile leaves are a liability they part with as cold and windy weather approaches. Evergreens, on the other hand, meet winter with different defenses. Many have thin, needled foliage that cuts down on wind-breaking surface area. Another frequent characteristic of evergreen foliage is a moisture retaining, wax-like outside coat. However, sometimes an evergreen’s natural defenses aren’t enough, especially in the context of the urban landscape where trees and shrubs are often overexposed to wind and sunlight.
What’s the solution?
To prevent winter drying, we recommend the application of an antidesiccant – a mild substance that forms a thin, transparent film on and under leaf surfaces (mimicking one of the trees’ natural defenses).This film acts as a moisture barrier, dramatically slowing the outward movement of water from a tree’s foliage. Additionally, antidesiccants help minimize sunscald, which is a condition resulting from white surfaces (i.e. anything covered in snow) reflecting sunlight onto, and ultimately burning, the foliage of a tree.
If there are evergreen trees and shrubs on your property, have them assessed for an antidesiccant treatment as soon as possible. The applications wear off naturally and in some cases, such as with arborvitae, should actually be applied twice, once in the late fall and again in late winter, to properly ensure against damage. Other common trees and shrubs susceptible to desiccation in our area include: hemlocks, pines, spruces, rhododendrons, azaleas, pieris, laurel and holly.
There are also more extreme preventative measures you can take for winter drying and sunscald, such as wrapping particularly susceptible trees and shrubs in burlap for the winter season, that an arborist might prescribe for your property. Watering practices are also important to staving off winter drying. Thoroughly soak susceptible evergreens in late fall, and water them during the winter if there is a warm period or an extended dry spell.
