by Don Janssen, Extension Educator
When temperatures drop and the cold wind blows, we throw an extra blanket on the bed to keep us warm. If we think we're doing the same thing when we apply a winter mulch to garden and landscape plants, we may be doing the right thing for the wrong reason.
In most cases, the aim of a winter mulch is not to keep the ground from freezing but to keep it from alternately freezing and thawing. This can injure plant roots and push plants and bulbs right up out of the soil. The exceptions are roses and strawberries.
In roses, the aim of winterizing -- covering the plants with mulch or rose cones -- is to protect the graft union from freezing and thawing. The graft union is the place where the named variety, the flowering part, was grafted onto the rootstock. If that part isn't protected, the top part may be killed.
Though strawberries are vulnerable to frost heaving, they need a winter mulch to protect the flower buds that will become next year's fruit crop. Mulching protects the flower buds against temperatures below 15 degrees F, which can damage or kill them.
Mulch strawberries after plants stop growing. Applying mulch before growth stops may smother the crowns. You need to apply mulch before temperatures drop below 20 degrees F, however.
As the name suggests, one of the best mulches for strawberries is straw. Other possibilities are chopped cornstalks, hay, corn cobs and bark chips. Grass clippings and leaves are not recommended because they tend to form thick, smothering mats. Each bale of straw should cover an area about 10 by 10 feet to a depth of 3 to 5 inches.
For perennial and bulb beds, chopped leaves and compost are good because they insulate the beds but plants can push up through them in the spring. Bark chips are often used around trees and shrubs.
A properly mulched tree has mulch over the root zone but not lapping up against the trunk. Mulch piled around the trunk could provide cover for mice and enable them to gnaw on the bark and girdle the plant.
Strawberry plants need to be uncovered as soon as they begin growing in the spring. Rake the mulch between the rows where it will be handy in case a freeze or frost warning makes it necessary to re-cover plants. After the danger of frost is past, it can be spread between rows for a summer mulch to help control weeds and slow the loss of moisture from the soil.
Mulches in flower beds and around landscape plants reduce the need to water and keeps lawn equipment at a distance. Injured bark on woody plants can give insects and disease organisms a place to invade.
Mulching to retain soil moisture is especially important around newly planted ornamentals, which tend to have limited root systems for the first year or two after planting. This makes them more susceptible to drought stress than established 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