| |
WRAP YOUR MAPLES NOW TO PREVENT SUNSCALD
I get calls each spring from folks distressed over splits in the bark of their maples and other thin-barked trees (e.g., cherry, crabapple, honey locust, linden, maple, mountain ash, plum). The problem, most often, is sunscald.
Sunscald is characterized by elongated, sunken, dried or cracked areas of dead bark, usually on the south or southwest side of a tree. On cold winter days, the sun can heat up bark to the point where cambial activity is stimulated. When the sun sets, or is blocked by a cloud, hill or building, bark temperature drops rapidly, killing the active tissue. As a result, the bark splits open, exposing the wood.
Young maples seem to be the most susceptible. Also, trees that have been pruned to raise the lower branches, or transplanted from a shady to a sunny location, are also sensitive because the lower trunk is no longer shaded.
Older trees are less subject to sunscald because their thicker bark can insulate dormant tissue from the sun's heat, ensuring that tissue will remain dormant and cold hardy.
Sunscald can be prevented by wrapping trunk with a commercial tree wrap, plastic tree guards, or other light-colored materials. The wrap will reflect the sun and keep the bark at a more constant temperature. If you haven't already wrapped your young maples and other susceptible trees, do it this week and leave the wrap on until late April or early May. Thin-barked trees should be wrapped for at least five winters after planting.
Tree wrap fabric is available at Chaska Farm and Garden, Chaska Building Center and other area garden stores. Start the wrap at ground level and wind it around the trunk so it overlaps. By starting at the bottom, the overlapping seams will shed, rather than collect, moisture from rain and melting snow. Extend the wrap up at least six feet or until you reach the lowest branch.
If you have sunscald damage from previous winters, you can repair it by cutting the dead bark back to live tissue with a sharp knife. Follow the general shape of the wound, rounding off any sharp corners to facilitate healing.
I've mentioned winter tree and shrub damage from animals in previous columns but it bears repeating. Rabbits, deer, mice and other rodents will feed on whatever tender twigs, bark and foliage of landscape plants that taste good and they can reach. They can girdle trees and eat shrubs to the ground in a single night.
The best defense for rabbits and rodents is to protect trees with a cylinder of 1/4-inch mesh hardware cloth around the trunk. The cylinder should extend 2 to 3 inches below the ground line for mice, and 18 to 24 inches above the anticipated snow line for rabbit protection. Hardware cloth can be left on year-round, but it must be larger than the trunk to allow for growth. For small trees, plastic tree guards are also affective.
Some gardeners have had success with various repellents concocted from rotten eggs, ammonia or other offensive substances. Most garden stores sell several brands of these repellent-type products. The most effective repellents for rodents contain thiram, a common fungicide. Most of these products need to be re-applied after heavy precipitation.
One more winter threat to trees, shrubs and perennials is salt. Salt used as a de-icer on driveways or sidewalks can damage or kill lawns and other plants when it is shoveled or blown away after a snowfall.
NOTE TO READER: More current research at the University of Minnesota suggests that a better strategy for protecting maple trees from sunscald is to place an 8-inch or 12-inch plank on end on the southwest side of the tree trunk. Plank should be put in place in November and removed in April. The southwest-facing plank will absorb and deflect the sun's rays so they don't heat the trunk of the tree.
|
|
|
 |
| |
|
 |
| |
PUTTING DOWN ROOTS:
A Delightful Blend of
Gardening Wisdom, Wit
and Whimsy
$10 + $2 for shipping
by Cliff Johnson |
 |
 |
| |
|
