CORVALLIS, Ore. – The Arctic blast that recently chilled much of Oregon might make you worried about your plants.
Ross Penhallegon, a horticulturist with the Oregon State University Extension Service, advises several ways to protect your landscape from frigid conditions.
"Insulation is the key thing for people to think about," said Penhallegon, a horticulture professor in OSU's College of Agricultural Sciences. "The biggest issue is that it's only December. This is the first of many cold spells. We still have the rest of December, January, February, parts of March and even longer in eastern Oregon in which we could still see some potential damage."
"Mulch, compost, leaves and any kind of organic matter will protect root systems. Snow can also be a tremendous insulator for many plants," he added.
Below are more of Penhallegon's tips to shield your garden from frost.
- Though snow can act as excellent mulch on the ground, it can also weigh down the branches of shrubs with frail structures, such as arborvitae, boxwoods, young rhododendrons and azaleas. Every two to three days, knock the snow off branches and wrap rope around the branches of bushes and shrubs. The branches of bushes and shrubs can be completely restructured. Tying the branches upward helps restructure the branches to a more upright position before the storm.
- "Rhododendrons are hammered right now particularly because the frozen ground," Penhallegon said. That's because there's no water available to move needed moisture and nutrients from the roots to the leaves and to other tissues throughout the plant, he said. Thirsty rhododendron leaves will look floppy and weak until the temperatures move above 32 degrees and the ground thaws. A mulch of leaves or snow, or compost, can help insulate root systems, allowing water to move from the ground and into the plant most of the winter.
- It's especially important to protect container plants since the pots can freeze, Penhallegon said. Cover them with compost, mulch, old blankets, or anything that can help insulate them. Don’t leave pots hanging. Place on the ground and cover.
- Most trees go dormant in the winter and can withstand temperatures in the negative degrees. The exception? Non-native trees that do not have the same cold tolerance as native trees. Be sure to plant trees with cold hardiness such as most tree fruits, Douglas fir, spruce, birch, and maples.
- 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, Penhallegon said.
- Keep your greenhouse above 35 degrees and plants inside will likely survive, Penhallegon advised.
- 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, Penhallegon said. Remember that this cold spell 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, Penhallegon said. 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.