Trees & Shrubs
UNL Extension – helping you turn knowledge into "know how"
Winter Tough on Landscape Plants
by Don Janssen, UNL Extension Educator
Winter can be rough on landscape plants, especially species that aren't native to Nebraska. Some types of damage can be prevented, however, and fall's the time to do it.
Among the most common types of damage are freezing, frost crack, desiccation and physical breakage. Homeowners can prevent or minimize some types of damage by shading plants, shielding them against heavy snow loads and flying salt spray, and wrapping.
Freezing injury to woody plants most commonly affects species or varieties that are not completely hardy in northern climates. It may kill only the flowers and shoots, the roots or the whole plant. The best way to prevent freezing injury is to plant only species and cultivars known to be hardy here.
Injury by late spring frost can sometimes be prevented by shading plants. Keeping the warming rays of the sun off the plants can delay bud break by five to 10 days. This may be long enough to avoid damage to tender flowers and shoots. It is practical only with selected small plants, however.
Frost crack, or "southwest disease," usually affects young, thin-barked trees, particularly young, newly transplanted silver maple trees. The bark splits when a bright, sunny winter day is followed by a rapid drop in temperature. The outer bark cools and contracts faster than the inner tissues and splits open, usually on the southwest side.
Planting species that are not prone to the problem and wrapping or shading the trunks or newly transplanted trees can reduce the incidence of frost crack.
Desiccation is most common in broadleaved evergreens, though it can occur in narrow-leaved evergreens and even on the shoot tips of deciduous species. It occurs on bright, sunny winter days. The sun warms the foliage, which then loses moisture to the surrounding dry air. Because the ground is frozen, the roots cannot take up moisture to replace it and the foliage or shoot dries out.
Plant sensitive plants where a building, a fence or other plants will shade them in the winter or construct sun shields on the south and west sides of plants to prevent this injury. Making sure plants go into winter well watered also helps.
Damage caused by drifting salt spray from highway deicing efforts look much like desiccation. Some species -- including white pine, red pine and arborvitae, red oak and crabapples -- are very sensitive to salt injury. Burlap or canvas screens can protect them against salt spray. Planting salt tolerant species such as blue spruce, Austrian pine and honeylocust is another option.
Physical damage to plants can occur in the form of branches broken by a heavy load of snow or ice, frost heaving of young plants, and mechanical injury from snow removal equipment.
Wrapping the plants with twine or chicken wire may be all the support that is needed. Others may require more elaborate wood or metal snow shields. Avoid plants known for their tendency to break in storms and prune trees when young to eliminate weak, V-shaped crotches. This will reduce the likelihood of breakage.
To prevent heaving of newly transplanted young plants on clay or clay-loam soils, mulch fall planted trees and shrubs after the soil has frozen to prevent its alternately freezing and thawing. This can push the plants' roots out of the ground.
To reduce damage by snow removal equipment, plant trees and shrubs some distance from snow plowing routes. Clearly mark the location of small plants that might be hidden by a blanket of snow.
The best time to prevent winter damage to landscape plants is before you plant. At that point you can still choose a hardy plant and a suitable planting site that minimizes the need for winter protection. For plants already in place, prevention is the best approach -- there is no cure for dead or severely damaged plants.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office
Contact Information University of Nebraska-Lincoln in Lancaster County
Web site: lancaster.unl.edu
444 Cherrycreek Road, Suite A, Lincoln, NE 68528 | 402-441-7180