University of Illinois Extension


Bruce Spangenberg
Extension Educator, Horticulture
Rockford Extension Center

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Preparing Plants for Winter

Weather extremes and wildlife damage are two main concerns facing landscape plantings during the winter season. While we are at the mercy of winter weather, there are some things that can be done to help prevent serious damage to perennial plants, trees, shrubs, and lawns.

Winter Mulching

Winter mulches should be applied to protect perennial plantings from winter weather. These are suggested to help protect perennial flower plantings and strawberry beds from alternating freezing and thawing cycles over the winter, not from freezing. It’s best to wait awhile before mulching perennials and strawberries until about Thanksgiving or later so plants have gone dormant and the soil freezes to apply the mulches. Straw or evergreen boughs make good winter mulches.

For most perennial flowers, allowing the dead plant material to remain until spring may help protect the crown of the plant, although if the bed is mulched later this fall it doesn't really matter. Most ornamental grasses provide interesting winter foliage effects when left standing.

Protecting Plants from Gnawing Damage

Rabbits and voles (field mice) are the primary animals that may gnaw on tender bark of trees and shrubs in winter. Putting up a barrier, such as poultrywire or hardware cloth, is the best defense. Put a fence around shrubs, and secure with a few stakes. Put a loose cylinder of hardware cloth around the trunk base of younger trees susceptible to vole or rabbit gnawing. Removing excess vegetation and debris near plants will also help reduce cover, especially for voles.

Repellents are also available to help protect plants from gnawing animals. Research studies have concluded results vary depending on location and even the specific year when using repellents. However, there are some important points to consider. Keep in mind repellents will reduce but not eliminate animal damage to plants. A good chickenwire barrier may eliminate rabbit damage to shrubs, but a good repellent may simply reduce the damage. So if some damage occurs, don't blame the manufacturer, as damage may have been reduced but not eliminated. Remember results vary considerably in studies.

There are two types of repellents, contact and area. Contact repellents are applied directly to plants and repel by unpleasant taste for the animal. Some product examples include DeerAway, Ro-Pel, Miller Hot Sauce, and thiram (a fungicide). Area repellents are applied in the vicinity of plants and usually repel by smell. Examples include Hinder, dried blood, bar soap, and human hair.

Research studies show not every repellent works in every situation, but contact repellents are more effective than area repellents. Commercial products appear more effective than "home-made" remedies. If you're planning to use a repellent this winter to protect shrubs and trees, read the labels thoroughly. Most need to be reapplied during the winter. Consider fencing or other barriers for more dependable protection - even though the initial costs are higher, remember they can be reused.

Preventing Winter Desiccation

Another problem facing evergreens during winter is desiccation, or drying out, from the wind and some cases sun. It's important that evergreens have adequate moisture in the soil right up until freezing. Monitor conditions throughout the fall to assure evergreens have adequate moisture available. Shrubs in very exposed sites may benefit from additional protection. Options include loosely wrapping with burlap, putting up a snowfence or other type of windbreak, or using commercially available antitranspirants, which are wax-like materials sprayed on plants late in the fall to help prevent drying out. These work especially well on broadleaf evergreens.

Lawn Preparation

Last winter was a very tough one for lawns. Snow mold (a fungus) and vole damage were both very high. Voles will make runways under the snow in lawns as they feed on grass blades and roots and are protected from predators. Help prevent damage from occurring by continuing to mow lawns until grass is completely dormant in fall. Mow lawns at a final height of about 2 inches. Also clean up any excessive vegetation near lawns, as this provides cover for voles.

Both gray (Typhula blight) and pink snow mold (Fusarium patch) may occur in northern Illinois. During the wet, cold weather of early spring, snow mold may be highly visible as matted, crusty looking areas. As conditions dry out, snow mold will gradually fade but infected areas may remain as weak or even dead turf. Conditions favorable for snow mold include excessive use of fast-release (water soluble) nitrogen fertilizer in early to mid fall, excessive thatch, shade, poor drainage, and excessive debris (such as leaves or straw) on the lawn. Areas receiving drifting snow or piles of deposited snow are also prone to snow mold.

There are ways to avoid snow mold from becoming a severe problem. Follow sound fertilization programs, using fertilizers containing slow-release or controlled-release nitrogen. Adequate levels of phosphorus (P) and potassium (K) should be available in the soil. Manage thatch via aerification, or removal from vertical mowing (dethatching). Improve air circulation by pruning or removing dense vegetation bordering problem lawn areas. Mow lawns until completely dormant in fall. Fungicides are available but rarely suggested for home lawns.


October - November 2001: Preparing Plants for Winter | Heating with Wood Needs Care and Consideration | Amaryllis for Winter Beauty | Understanding Fall Color |

Past Issues

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