By Robert Tigner
SW 4 Agricultural
In early December, we experienced about a 60-degree difference in temperatures from one week to the next. Sudden temperatures drops can injure plants when they are not fully dormant.
Since most established turf areas had hardened off quite a while prior to the extreme temperatures, little negative effect is expected.
Kentucky bluegrass seeded prior to late September should have established well enough that no or very little damage will occur.
Late seeded (after Sept. 15) tall fescue and perennial ryegrass may not have established well enough to avoid injury. These turfgrass species are most susceptible to cold temperature kill or desiccation on exposed sites (prior to snowfall). Snow cover will help insulate new seedlings against temperature extremes and also reduce injury from desiccation.
Foot or vehicle traffic on frosted or frozen turf can cause cosmetic damage resulting in foot prints, pathways or tire tracks across the turf that may not recover until late spring.
Woody plants prepare for winter through a process called hardening off. They reach their peak cold hardiness in mid-winter. To promote hardening off and reduce the risk of cold temperature injury, avoid over watering trees from mid-August until after fall leaf drop; and do not apply nitrogen fertilizer after mid- to late July.
Most woody plants had likely hardened off enough by December so little damage occurred from the area’s extreme temperatures; however, tree species or cultivars not fully hardy to Nebraska, or those that were over watered or fertilized after July, may experience injury to their cambium layer resulting in bark sloughing off and general tree decline.
Extreme cold, drying winds, bright sunlight or a sudden drop in temperature are common causes of winter injury to trees and shrubs. The frequency and severity of winter damage is determined by a number of factors including the plant species or cultivar, the location and conditions under which the plant is grown, and timing of the weather extremes in the dormant period.
Ice and snow build-up on trees can lead to limb breakage or less obvious splits and cracks. However, if snow or ice builds up on the branches of deciduous trees and shrubs, do not hit the branches to knock the accumulation off. Carefully brush snow off of snow-laden branches but leave ice to melt naturally.
Trying to knock ice off may result in branches breaking or cracks occurring. If branches of evergreen trees and shrubs become heavily weighted with snow, this too can be carefully and slowly brushed off.
When it comes to ice, let it melt naturally. As long evergreen branches are not broken, they usually return to a normal position with time.
When heavy snow or ice damages a tree, questions about whether the tree can be saved or not arise. A tree may appear ruined, but could recover in time with professional pruning by a certified arborist.
The Nebraska Forest Service states that if a tree is uprooted, the trunk has completely failed or more than 50 percent of the branches are broken, the tree is not salvageable.