With our crazy Kansas weather, winter may seem more like summer. Highs in the 70s during February may feel nice, but when lows drop to the teens at night, these temperature swings may cause serious damage to the trunks of trees. This damage is known as sunscald and typically occurs on young thin-barked deciduous trees like maples, birch, poplar, oak, and 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 sun onto the tree.
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 causes the cells to rupture and die. This not only causes direct injury, but also stresses the tree making it more susceptible to insects and fungi. Sunscald is predominantly found on the south and west side of trees as these are areas that receive direct sunlight in the winter months.
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 fungi attacks. The good news is 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 trunk of the tree with crepe paper which can be found at most home improvement store garden centers. When wrapping the tree, start at the base of the trunk and wrap the tree overlapping each wrap by one-third. Idealy 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 placing a removable fence to shade the trunk, or for non-ornamental trees (such as an orchard), white latex paint can be painted directly on the trunk to reflect the light.
Remember to remove the wrap in the spring! If you forget, the warp can harbor insects and mold!
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