With our crazy Kansas weather, winter may seem more like summer. Highs in the 70s in February may feel nice, but when lows drop to the teens at night, these temperature swings can cause serious damage to tree trunks. This damage, known as sunscald, typically occurs on young, thin-barked deciduous trees such as maples, birch, poplar, and oak, as well as on fruit trees. Even when air temperatures are below freezing, the surface of the tree may be significantly warmer, especially if snow, a parking lot, or a building reflects the sun onto the tree.
Sunscald
Sunscald is caused by the sun warming the bark of a tree during the winter months. This causes the tissue to break dormancy and begin transporting water from the roots to the branches. After the sun goes down, temperatures fall, and ice crystals form in the cells. The ice ruptures the cells and causes them to die. This not only causes direct injury but also stresses the tree, making it more susceptible to insects and fungi. Sunscald is most common on the southwest side of trees, as these areas receive direct sunlight in winter.
Prevention
Once sunscald has occurred, there is nothing that can be done other than trying to increase the tree’s vigor to ward off insect and fungal attacks. The good news is that sunscald prevention is simple, cheap, and can be done by a homeowner without the aid of an arborist. The easiest option is to wrap the tree trunk with crepe paper, which is available at most home improvement stores and garden centers. When wrapping the tree, start at the base of the trunk and wrap the tree, overlapping each wrap by one-third. Ideally, this should be done in November and removed around Easter, and should be done for at least the first two years after planting. Other acceptable methods include installing a removable fence to shade the trunk, or, for non-ornamental trees (such as an orchard), white latex paint can be applied directly to the trunk to reflect light.
Drought-stressed trees are also more susceptible to sunscald, so make sure to water them if the weather is dry and the ground is not frozen.
Remember to remove the wrap in the spring! If you forget, the warp can harbor insects and mold!
