Experts with Oregon State University Extension Service recommend several ways to guard your landscape from frigid conditions.
Although snow can act as excellent mulch on the ground, it can weigh down the branches of shrubs with frail structures, such as arborvitae, boxwoods, cypress, young rhododendrons and azaleas.
Knock off the snow on branches and wrap rope around them. Tying the branches upward helps restructure them to a more upright position before the storm. Leave snow at the base of plants, however, because it insulates roots.
Insulate tender perennials—including hardy fuchsias, roses, clematis, salvia, some ferns, canna, agapanthus and dahlias—with mulch, compost, leaves, conifer branches or any kind of organic matter that will protect root systems.
For extra help on plants you particularly prize, use this trick: Assemble a tomato cage—the square, folding types are best—around it. Wrap burlap around the outside of the cage, and secure it with bungee cords. Fill with straw or leaves. Remove the material when the temperature rises.
It’s especially important to protect container plants because the pots can freeze. Pull them into an unheated garage, basement, greenhouse, cold frame or similar site. Make sure it’s a place where the temperature stays above freezing.
If you have no place indoors for plants, safeguard them by covering with evergreen boughs, straw, leaves, old blankets, sheets, burlap, woven row cover, sheets of plastic or anything that can help insulate them.
Wrap pots in bubble wrap to provide even more protection. Don’t leave pots hanging. Place on the ground and cover.
If you don’t know the hardiness of your plants and have lived in the same place for more than a few years, think back to which plants limped through winter and concentrate on those.
Most trees go dormant in the winter
and can withstand temperatures in the negative degrees. The exception is nonnative trees that do not have the same cold tolerance.
Be sure to check labels before buying and make sure to plant trees with cold hardiness appropriate to your area. Check the USDA plant hardiness zone map at http://planthardiness.ars.usda.gov to find your hardiness zone.
Don’t walk on your lawn, especially if there is no snow insulating the grass. Walking on it can break the leaf tissue and damage the grass if it is frozen.
Keep your greenhouse above 35 degrees, and plants inside will likely survive.
Next spring, you may notice some brown freeze streaks and damage on the leaves of the spring-flowering trees and bulbs you put in the ground recently. Cold weather likely will cause a lot of leaf and tissue damage. Frost damage causes leaves to appear water-soaked or shriveled, or to turn dark brown or black, but does not always kill the plant.
Generally, do not water your plants in freezing conditions. But shrubs growing underneath the eaves of a house are susceptible to drought damage. Water them deeply every six to eight weeks only when the air temperature is above freezing and early in the day.