Sunscald may sound like something that happens in hot weather, but on trees and ornamentals it is a cold-weather problem, occurring in winter and early spring. Tender bark on a southern surface warms much more from winter sun than the bark on the northern surface. The temperature of dark-colored bark in particular is raised considerably by the sun's rays. If a chilling breeze comes along or a cloud suddenly covers the sun, the mercury falls rapidly. The sudden drop in temperature can make the plant cells rupture, causing damage to the bark. Damage that occurred in winter might not be apparent until spring. Sunscald is particularly noticeable on young trees planted where daytime heat is high, such as beside a wall that reflects the sun's heat, or on the south side of the trunk. In warm weather, light-colored mulches can also reflect heat onto tree trunks. As a result parts of a tree, or even the entire tree, can be damaged. This is especially true for young trees. Bacteria or insects may enter the damaged bark and cause further problems.
Sunscald on trees can be prevented by wrapping the trunks with a commercially available tree wrap or with burlap or agricultural fleece. You can also guard against sunscald by painting the bark of young trees with white interior latex paint mixed with water 1:1, in the fall. The light color reflects the sun's rays and prevents sudden temperature changes. Using dark-colored mulching material that will absorb the sun's heat, rather than reflecting it onto the tree's trunk.
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