Fall is a critical time for plants to rehydrate themselves, and evergreens especially need to be well hydrated going into the winter season. After experiencing a dry fall, it is even more important to spend some extra time preparing your evergreens for the drying effects of winter weather.
The parts of an evergreen that are above the ground are continuously losing water in a process called transpiration. Once the ground is frozen, the plant’s roots will not be able to take up water to replace the moisture that is lost through the top.
Winter desiccation is sometimes referred to as winter burn or winter browning. Desiccation occurs when the evergreen’s foliage loses moisture due to the bright winter sun and harsh winter winds. Evergreens that have just been planted this fall will be the most susceptible to winter injury from desiccation. Those plants situated in a sunny, windy area will lose moisture more rapidly than those in a more protected area. Broad-leaved evergreens, such as rhododendrons and boxwoods, are even more susceptible to drying out, as they have a greater leaf surface to lose moisture from.
If the fall season is a dry one, water thoroughly every seven to 10 days, applying at least an inch of water each time. The best time to water is in the early morning, finishing by around 8 a.m. At times it may be more convenient to do the watering in the evening hours, but doing so can make plants more susceptible to disease infection by providing the moisture that fungi and bacteria need to grow.
While some roots grow deep, others known as feeder roots, which are responsible for the bulk of the water intake, are in the top 12 to 18 inches of the soil. The majority of these feeder roots are located not at the trunk but at the drip line and beyond of the plant. Watering should be aimed at the feeder roots and allowed to thoroughly soak at a slow rate for best penetration. Apply a 2- to 3-nch layer of mulch to retain moisture and to protect the roots from heaving during the winter on newly planted stock.
Anti-transpirants are available at garden centers and can be sprayed on plants after winter arrives. These products create a thin film over the leaves and stems and reduce the amount of water that can evaporate from these tissues. Check the product label for reapplication information. They often must be reapplied during the winter because they tend to break down over time and lose their effectiveness.
You can also provide some wind protection by loosely wrapping the evergreen with burlap or protecting the windward side of the evergreen with a burlap screen easily made with a strip of burlap and a number of stakes.
Some evergreens, such as arborvitae and junipers, are also susceptible to breakage from snow and ice build-up. Before that kind of weather sets in, loosely wrap these plants with rope or twine to keep all of the branches tied together to prevent splits and breakage. You can also gently shake your shrubs to remove snow so it does not continue to accumulate and cause damage.
Voles have been known to girdle small trees during the winter in search of a meal. They often target the tender bark of young trees. To prevent this damage, install a wire mesh cylinder around the base of the tree. Bury it about three inches into the soil and make it about 18 inches high or higher than the average snow line level.
Here are just a few evergreen facts for you: evergreen needles have different life spans, depending on the specie, white pine and arborvitae will drop their two-year-old needles in the fall, spruce needles will live anywhere from three to 10 years and broad-leaf evergreens like the rhododendron, will drop their two- to three-year-old leaves in late summer and early fall.
As always, Happy Gardening!