Winter burns plants

KENNEWICK -- Gardeners with spring fever are getting out in their yards more -- when the days are warmer and sunnier.

Many are noting with dismay brown or dead foliage on their needled and broadleaf evergreens. Some assume that it's the affect of the severely cold temperatures we had in early winter.

Others aren't sure and are bringing in samples for me to check for signs of life.

Most of the evergreens with brown or bleached needles or leaves are suffering from a problem called winter burn. It's called "winter burn" because it looks like the foliage was scorched by fire.

Winter burn would be more correctly named "winter drying damage." Winter burn happens when wind and sun cause increased water loss from the leaves. If the soil is frozen from cold temperatures, the water in the leaves can't be replaced and dehydrated leaf tissues die and turn brown.

Winter burn tends to be worse on the side or sides of an evergreen exposed to sun and wind. These conditions increase water loss through the leaves and lead to more severe winter burn.

Winter burn also will be worse on plants that were drought stressed going into winter or if the soil was dry in early winter before the soil froze. It is important to remember to water evergreens in fall and winter months when the soil isn't frozen and the weather is relatively mild. Evergreens are susceptible to drought stress at these times because they still are losing moisture through their needles and leaves even though they appear dormant.

Evergreen trees and shrubs planted in mid to late fall are particularly vulnerable to winter burn because they experience stress from root injury that occurs during the planting process. In addition, if the weather turns cold soon after planting, they don't have enough time to replace damaged roots and are unable to absorb enough moisture from the soil. It's especially important that the soil in the root zone of recently planted evergreens be kept adequately moist throughout mild fall and winter weather.

Our region has been coddled by relatively mild winters for a number of years in succession. Perhaps a perceived regional climate change has lulled us into thinking that winter burn and winter damage from cold temperatures were a thing of the past, but periods of severe cold this winter have resulted in winter burn on many local pines, arborvitae, Chamaecyparis, boxwood, euonymus, rhododendron and other evergreens.

What can we do? Some of the plants I've looked at appear to have healthy buds and new growth will develop normally when spring arrives. The damage promises to be more severe on others, such as boxwood, where entire twigs and branches may be dead. Sit tight and be patient. See if new growth begins to grow with the arrival of spring. When it does, prune out all dead growth.

Are there other gardening problems you would like an answer from me about? I'm on the Spring Garden Day program March 5, and will be answering garden questions in an open forum. I also will be available afterward to answer your questions one-on-one.

Spring Garden Day is a daylong program filled with gardening classes for local gardeners with spring fever who want to learn more about gardening in the area.

Sponsored by WSU Extension and the WSU Master Gardeners, the cost is only $20 to learn from local experts about gardening.

To register, call the WSU Extension Office at 735-3551.

* Marianne C. Ophardt is a horticulturist for the Washington State University enton County Extension.