Friday, January 30, 2009
Saving trees from the effects of winter weather
John Arbogast
Landscape consultant John Arbogast answers your questions every Thursday. Send questions about your lawn, garden, plants, or insects to:
Dear John
5102 Greenfield St. SW
Roanoke, Va. 24018
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Q: I live in a semirural area of central Virginia and need answers about what this winter weather is doing to my trees on my two acres. The trees are mostly evergreens, but I have some deciduous shade trees on the property. The trees have been planted during the 10 years since we moved here. I spread organic mulch around the trees last summer and fall. I would like to know if the mulching is OK due to this winter’s wet weather and what, if anything, I should do about it. What I should do about possible rodent damage to the trees? A neighbor lost several young trees to bark chewing a few winters ago.
A: I got a lot of information from the Virginia Cooperative Extension publication “Managing Winter Injury to Trees and Shrubs,” revised by Doctors Diane Relf and Bonnie Appleton.
Mulching young trees and shrubs is a good thing during the winter if done correctly. As the Extension publication states, winter mulching acts as a buffer to the soil by reduceing the amount of alternate freezing and thawing of the soil that causes frost heaving of root systems.
However, too much mulch can hold too much water from rains and melting ice or snow. Mulch also gives easy access for certain rodents to soft, moist bark that they like.
Examine the amount and pile of your mulch. It should be shaped like a saucer with almost no mulch around trunks and tapered up to no more than 2 ½ inches under the branches.
Keeping organic mulch away from the trunks means there'll be no protected tunneling opportunities for rodents to reach soft trunk bark. This shape of mulch is referred to as “saucering” -- think of it like a giant coffee cup saucer with the low point in the center and then a higher rim.
Mice can cause serious damage to trees or shrubs. They chew off the bark at ground level or below and can completely girdle a tree, causing it to die. Most of this damage takes place during winter. Keep mulch pulled away from the base of the tree, and examine it frequently for the presence of mice.
In many home and commercial plantings, placing poison bait in their runways controls mice. These poisons and complete directions on how to use them are sold at any lawn and garden store.
Mice may also be controlled by trapping. This can be successful where only a few trees are involved. Peanut butter makes a good lure as bait for these traps.
Rabbits can also be responsible for the loss of young trees each year. Here's how to keep them away:
Cut a 36-inch wide roll of galvanized screen or "hardware cloth" with a ¼-inch mesh lengthwise, forming two 18 inches strips. By cutting these strips into pieces 14 inches long, guards 14 or 18 inches are created.
Roll the strip around the trunk of the tree so that the long side is up and down the trunk and the edges overlap. Twist a small wire loosely about the center to prevent the strip from unrolling. Push the lower edges well into the ground. This metal guard can be left in place all year.
Tree wraps can also be used in a similar manner, but must be removed in the early spring to prevent damage to the bark.
Other methods of rabbit control have been successful. Ordinary whitewash has given good results in some instances. Some commercial fruit tree growers use a repellent wash recommended by the United States Department of Agriculture that contains equal parts of fish oil, concentrated lime sulfur and water. Repellents under various trade names are available. All these materials may be applied with a paintbrush to the trunk of the tree from the ground up into the scaffold limbs.
