Fall is the time to to give your plants some tender loving care before Old Man Winter comes along to give them the shivers for the next six months.
Most perennials are preparing for winter by "hardening off," a process of gradual adjustment to cold weather. You can help them make it through the winter by mulching beneath shrubs and around tree trunks.
Mulches insulate shallow root systems and help prevent injury caused by freezing and thawing of the soil throughout the winter. A mulch also helps conserve moisture during long dry spells; in addition, mulches control weeds during the growing season, said James Feucht, Ph.D, Colorado State University Cooperative Extension specialist for landscape plants.
Use mulches that stay loose and airy, such as composted leaves, wood chips, chunk bark and coarse gravel. Avoid mulches that compact easily, such as native peats.
While your perennials are preparing for winter, your annuals are not. Remove them, roots and all, Feucht said. Lay them in windrows at the garden's edge and grind them with a rotary lawn mower. Move the mower back and forth over the vegetation in a way that will blow the chopped material back into the garden.
Plow this chopped material into the garden; it will decompose long before the soil freezes. Don't, however, chop and plow weeds. Their seeds will overwinter in the soil only to sprout up at the first sign of spring. Some weed roots propagate themselves, and will make a healthy -- if unwanted -- comeback next year.
Wrap trunks of recently planted trees, especially those with a thin bark. Use a commercial crepe-type tree wrap available at local garden centers. Honeylocust, green ash, fruit trees and soft maple particularly need this care to prevent a condition known as sunscald, according to Feucht. Sunscald is caused by a drying of the bark, usually on the southwest side of the tree. During the winter months, the sun is at a low angle and by mid-January, cells in most northern hemisphere plants have satisfied their dormancy requirements. These cells become active when warmed by the sun, but freeze when temperatures plunge at night. Tree wrap prevents these sudden and damaging temperature fluctuations.
Apply the wrap from the base up the entire length of the trunk to the second or third branch. Overlap about 50 percent as you wrap, so edges will shed water. Use a thumbtack or piece of tape to secure the wrap at the top. Remove the tree wrap in April; it will harbor insects and diseases if left on during spring and summer.
Don't be tempted to use a substitute such as strips of cloth or burlap. These materials absorb water, and water conducts both cold and heat. The commercial wraps are scientifically designed to insulate the trunk without creating additional problems.
For more information about preparing your garden and yard for winter, contact your local office of Colorado State University Cooperative Extension.
Photo: Judy Sedbrook
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010