The Forecast for Spring

Wisconsin certainly has highly variable winter weather from dramatic temperature swings, rain to snow and in between. These weather conditions being both good and bad within it.

Most of the problems that we find in early spring are environmental or physical in nature. Pruning is the best way to handle damage from the weather and small animals. As soon as the snow is gone from around the bases of trees and shrubs, scout for girdling at the bases of branches and trunks. If the girdling is NOT severe, often simply cutting out the damaged branches is enough to help renew the plant. Next fall, winter protection in the way of hardware cloth or other tree guards is advised. If entire trunks are girdled, generally consider the tree to be dead. While there may be ways to bridge graft the damage, it does not have a high rate of success. Put in a new tree and remember to protect them next fall

A frost crack is a long, deep, narrow crack running up and down the trunk of a tree. The crack is usually on the south or southwest side of the trunk but can occur on any side. Young trees or older trees with smooth bark are most susceptible.

The crack occurs when the sun warms the trunk in winter, causing tissues to expand. When clouds or buildings block the sun or at sunset, the temperature of the trunk drops abruptly to that of the surrounding air and the trunk contracts. The outer part of the trunk cools and contracts faster than the inner tissues. This difference in contraction rates causes the outer trunk to crack from the inside to the outside.

Prevent frost cracks by wrapping young trees with paper tree wrap. The wrap should start at ground level and go all the way up to the first main branches. Fruit trees are sometimes painted with white, latex paint, which reflects the sunlight and prevents the trunk's cracking.

Once a crack occurs, nothing can be done. Fertilizing a low vigor tree may speed up growth and close the crack more quickly. Frost cracks can allow rots or canker diseases to get established in the trunk. (Michigan State University Extension Home Horticulture - 01701142 )

Other problems you may notice may include brown spots in evergreens, or reddish foliage in the broadleaf evergreens such as rhododendrons and boxwood. The best way to prevent future damage would be to use an antidessicant product in the fall, or protect with a burlap wrap. The browning of needles on evergreens is generally attributed to winter injury. The damage is thought to be caused by a combination of desiccating winds, winter sun, and widely fluctuating temperatures. The dry conditions that have prevailed years may also have played a role. Browning of evergreen foliage can be seen on pines, yews, arborvitae, firs, and spruces. Damage is most evident on the south and west sides of trees and shrubs. The brown needles on affected trees and shrubs have been destroyed and will eventually fall off. Fortunately, the buds on most damaged evergreens are still alive and will break bud and produce new growth this spring. The affected trees and shrubs should look much better by late June or July. There is no need to fertilize affected evergreens. However, if the weather this spring is dry, periodically water the trees and shrubs to encourage new growth and speed their recovery.

Prepared by Richard Jauron, Department of Horticulture Iowa State University, Ames, Iowa.