As fall quickly turns to winter, temperatures are plummeting several weeks ahead of normal. Frost and snow blanket our landscapes. For annual plants, their nonhardiness is readily apparent. For them, putting the garden to bed is mostly a matter of cleaning and clearing out.
For trees and shrubs, nature has given them some excellent coping skills for dealing with winter. Deciduous plants evade the season: They drop their leaves, pull in their sap and snooze right through it. Evergreens endure the cold using a kind of antifreeze that lets them slow down and keep going until spring.
In spite of these natural defenses, you can still give your trees and shrubs a hand. Even the toughest plants are not immune to three of the most common challenges of harsh winter conditions.
Snow and ice load
When lots of snow accumulates quickly, it builds up on branches. The stress can deform or even break them off. But trying to remove it at the wrong time can do more harm than good. Resist the temptation to knock or beat snow and ice off with brooms, rakes or other hard objects. The impact could cause the wood to snap. Rather, gently brush or sweep it off instead.
To help all shrubs and trees stand up to snow loads, prune out thinner, weaker branches, as well as any that are rubbing against each other or growing at narrow angles.
If you live in areas that receive regular heavy snows, use plants that can endure the weight. Ginko, white oak, little leaf linden, Douglas fir and paper bark maple all have the strength and structure to take heavy snow loads.
Similarly, don’t attempt to remove ice after a freezing rain. The frozen, brittle wood could easily shatter and come crashing down on you. If the branch is bending badly, try supporting it temporarily with a sturdy length of wood.
Desiccation, also known as winter burn, causes an evergreen’s foliage to die off, often in just one exposed place or on a single side of the plant. A shrub in an exposed location, such as the southwest side of a building, has the moisture drawn from it by sun and wind. But because the soil is frozen, the plant’s roots can’t recover lost water, and the cells dry out and die.
Once it’s brown, evergreen foliage won’t come back. So in spring, prune these dead areas back to the first green shoots. New growth should eventually fill in the area.
To keep moisture in the plant, antidessicant sprays contain waxy resins that seal leaves and needles and prevent water loss without harming foliage. Apply to the most exposed sides of plants before the ground freezes. Sealing sprays break down in sunlight, so reapply every couple of months during winter. Spray when the temperature won’t drop below freezing for 24 hours.
The unsightly burned, dead area that opens the tree or shrub to infection is caused by this. It starts on clear, winter days when the temperature warms enough to get the sap flowing. When temperatures drop below freezing at night, the sap refreezes, expanding and splitting the cells of the bark. Young and newly planted trees and shrubs, as well as plants with thin bark like crabapple, cherry and maple, are especially susceptible.
Prevent sunscald by wrapping trunks with bark fabric or tape. They reflect the sun, keeping the plant at a more constant temperature. After the ground is frozen, wrap at-risk and new plants for at least the first five winters. Use a stretchy, loosely woven fabric that won’t girdle the plant if it’s left in place too long.
To treat existing sunscald, cut away the dead bark back to healthy green tissue. Follow the general shape of the wound, using a sharp knife sterilized in a solution of one part bleach to nine parts water. Don’t cover the cuts with pruning sealer or other wound dressings. Just let the tree develop scar tissue around the damaged area and heal itself naturally.
Joe Lamp’l hosts and produces “Growing a Greener World” on national public television.