Winterizing Trees and Shrubs
Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent
Avoiding drought
stress with adequate fall irrigation is also important in winterizing your trees
and shrubs. Be sure to give your landscape plants a deep watering before your
water supply is cut off for the season. Don’t
neglect watering the trees, especially birches, situated in your in the lawn.
Fall watering is
critical for the broadleaf evergreens, such as rhododendrons, and needled
evergreens, such as like pines and arborvitae, in your landscape.
They may not be actively growing, but evergreens still lose moisture
through their leaves and needles during the winter.
They’re prone to damage from winter drought... another reason to keep a
hose and sprinklers handy during the winter months.
Don’t let them go dry, especially during mild winter weather.
Fall fertilization
may also give some protection to trees and shrubs against cold winter
temperatures. If you decide to
fertilize your plants, place the fertilizer in the root zone area after they
have gone dormant, but before the soil in the beds drops below 45 degrees.
Mulching the root
zone of trees and shrubs is frequently recommended for weed management and to
help reduce the loss of moisture from the soil, but it can also provide some
insulation to tender root systems. This is particularly important for plants
that are only “borderline” hardy in this region, as well as for young or
recently planted trees and shrubs.
Loose mulches can
be applied to the root zone to provide some insulation from cold temperatures
and to moderate the effects of freezing and thawing. Apply a several inch layer of a mulch material that allows
good air and water movement. Use
mulches like shredded bark, pine needles, or coarse compost. Keep any mulch several inches away from the trunk of the tree
or shrub to discourage mice and to avoid problems from excess moisture close to
the base of the plant.
Trunks of young or
recently transplanted trees can be protected against splits by shading the south
and west sides of the trunk. Some
gardeners shade the trunk of their trees with a commercial bark wrap or they
simply use a board on the sunny sides. The
shading or wrap keeps sunlight off the trunk, preventing the bark from warming
up too much on a cold winter day and reducing temperatures fluctuations that can
lead to trunk or bark splitting.