North Dakota State University -- NDSU Agriculture Communication
7 Morrill Hall, Fargo ND, 58105-5655, Tel: 701-231-7881, Fax: 701-231-7044

September 23, 2003


Get Trees Ready for Winter, Forester Advises

Fall is a favorite time to enjoy trees and their foliage. Itís also a critical time for taking care of them, says a forester at North Dakota State University.

AFall is a great time to plant certain trees and prevent problems that can result from winter conditions," says Joe Zeleznik of the NDSU Extension Service. "North Dakota winter conditions can be hard on trees, but there are some simple things that we can do to minimize problems."

Both fall and spring can be good for transplanting trees, but it's a little trickier in the fall, Zeleznik says. "It depends on the type of tree and the type of planting stock. For example, most hardwoods can be transplanted in the fall after they are dormant without much of a problem. Hackberry actually does better with fall transplanting than it does with spring transplanting."

Conifers are more sensitive to fall transplanting. When transplanting conifers in the fall, keep as much of the root system as possible, and don't transplant too late (before mid-October), Zeleznik advises. Otherwise, the trees may be susceptible to winter injury because they haven't had a chance to bring in enough water before the soil freezes. As always, water the new trees thoroughly. This will help the soil settle around the roots, eliminating air pockets.

"For those who have had problems with apple scab or ash anthracnose, raking fallen apples and leaves and disposing of them is very helpful in minimizing or eliminating these diseases," he says. "Both of these are fungal pests and spend the winter in the fruit and leaf litter, releasing new spores in the spring. By eliminating the winter habitat for the fungus, you stop it from reinfecting your trees next spring."

Another problem that may occur is winter injury of evergreens, a concern that was particularly prevalent in the region last winter. "Colorado blue spruce and Black Hills spruce are especially susceptible to winter injury," he says. The problem occurs on warm, sunny days in late winter when trees lose water from their needles. However, they canít replace the water because the ground is frozen.

"To help minimize the problem, be sure to water your spruce trees until the ground freezes up," Zeleznik says. "If your water is saline, donít use it because it may worsen the situation." Be sure to winterize your outside spigots and pipes once this task is complete.

A third winter malady is sunscald. "Contrary to its name, sunscald is actually a freezing injury that occurs on the base of thin-barked trees on calm, sunny days," Zeleznik explains. "With these weather conditions, the bark will warm up and the growth layer beneath it, the cambium, will become active. If the sun goes behind a cloud or sets very quickly, the temperature will drop rapidly and the active cambium will freeze and die." To prevent the problem, wrap a piece of white plastic around the base of the tree, to about 2 feet high.


Source: Joe Zeleznik, (701) 231-8143,
Tom Jirik, (701) 231-9629,