Weather Forecast


Start protecting trees for winter now

Minnesota winters may be as stressful on trees and shrubs as they are on humans. Plants may suffer from root or stem damage, frost cracks, winter browning, die back, bud death and even plant death.

Each spring, we get scores of calls on damage to newly planted trees. In many cases, the trees were near the point of bearing fruit and such a loss is both frustrating and discouraging.

Young trees are vulnerable to two preventable problems each winter, sunscald and critter damage. Luckily, both types of damage are easy to prevent with a little work and inexpensive materials.


Sunscald and bark cracks occur mostly on the south and southwest sides of smooth barked trees and shrubs. Young maple, apple, aspen, linden, mountain ash and azalea are most vulnerable. With sunscald, temperature changes cause water that thawed in the tree to suddenly freeze, killing the cambium layer. There is a sloughing off of outer bark. Extremely cold temperatures and water-stressed trees suffer vertical frost cracks.

Use of slow-release nitrogen based fertilizers at LOW rates may help reduce stress and help plants recover in the spring.

Provide shade with other plants or structures on the south sides of vulnerable trees and shrubs.

Stem protection such as wrapping young trees in the fall may help some plants. Start at ground level and work up to the first branches; remove the wrap in spring if using the disposable wraps.

Light-colored, loose stem protectants are most effective.


Mulching around the tree's base reduces soil moisture loss, improves water and air penetration, and keeps soil temperatures more stable. These conditions are helpful for root growth and therefore improve tree vigor. Wood chips, shredded bark, dried grass clippings or pine needles all can be used for mulch. Cover the area with mulch about 3 to 4 inches deep. Avoid mounding mulch next to the tree trunk.

Critter damage

Protection from rodents and rabbits must be in place before damage occurs. Little can be done after they have girdled your prize apple tree!

Tree trunks can be protected from the damage of voles, mice and rabbits by placing a cylinder of quarter-inch-mesh hardware cloth or plastic drainpipe around the trunk. It should extend two to three inches below the ground line for mice control and 18 to 24 inches above the anticipated snow line for rabbit control.

This protective ring should be removed each spring, or at least evaluated to ensure that it does not end up girdling the trunk as the tree grows.

You can protect shrub beds from rabbit feeding by fencing the beds with chicken wire. Check fenced areas frequently to ensure a rabbit has not gained entrance and is trapped inside.

Trees add tremendous value to a homeowner in a variety of ways. A small amount of effort this fall can prevent disappointment and unnecessary work and expense next spring with a few simple measures taken this fall.

For more information, contact me at the Polk County Extension office in McIntosh at 800-450-2465, or at the Clearwater County Extension office on Wednesdays at 800-866-3125. If e-mail is your thing, contact me at

Source: University of Minnesota Forestry.