Cold injury, the damage caused by freezing temperatures, can occur on fruit, stems, leaves, trunk and roots. Water inside these plant parts can freeze and expand, tearing cell walls causing them to leak. This damage may go unnoticed until the plant fails to come out of dormancy in the spring.
There are three types of cold injury. The first I call a burn. Often times, cold damaged plant parts will become mushy and turn brown or black. Over time, the damaged leaves or stems will dry out and appear to have been burned with a torch. Sunken areas may appear on branches and trunks and the bark may peel.
The second type of cold damage, desiccation, can be caused by winter winds. Cold air does not hold moisture like warm air (thus summer humidity and winter dry air) and can dehydrate plants if it is sustained for long periods of time. Leaves may dry up at the edges and eventually turn completely brown.
The third type of winter damage is wood splitting or frost cracks. This damage occurs on stems and branches. On particularly cold nights, water in the cells just beneath the bark of trees and shrubs freezes. When the sun hits these areas the next day, the water thaws quickly killing the cells and splitting the wood. Eventually, longitudinal (lengthwise) cracks may appear. Often these are not evident until the following summer.
