THE TREE DOCTOR (aka The Plant Doctor)

Winter Injury on Trees and Shrubs

Despite the fact that the winter of 2001-2002 was considered mild, some of us are in for an awakening this spring. We witness winter injury every year, but winter injury manifest itself differently on different plants. During very cold winters, we observe cambial (vascular system) death in many plants, even some hardy ones. Cambial death often results in bud break and shoot expansion followed by sudden wilting because the destroyed cambium is no longer able to support the growth of the new shoots. During the past mild winter, the wide fluctuation in temperatures may result in bud death. If primary bud death is a problem, we can expect slow emergence and growth in the spring as secondary buds make up for the loss.

Alas, there will undoubtedly be some injury to trees and shrubs from rodents and animals. This injury may not be noticed for some time.

Winter injury due to adverse environmental conditions or animals is usually quite evident in the spring and early summer. Many of you have already noted some injury to many evergreen species during the late winter to the present. Several phone calls have queried whether this is some sort of needle cast or blight. Invariably the answer is “no”. Most evergreen trees and shrubs along Michigan’s roadways and streets exhibit browning of the foliage due to desiccation from wind and deicing salts. Even Austrian Pine, the standard for salt tolerance, exhibits abundant needle desiccation due to the record levels of deicing salt applied this past winter.

If desiccation is the problem, most of these plants should recover, particularly since we’ve had fairly abundant soil moisture over the past several months. Other forms of winter injury may yet be encountered whether from bud death or cambial damage, but different species react and recover differently from these problems. Watch for bud break and shoot development before you write off any plants. Most should recover just fine.