Overexposure to sun causes sunscald. The problem commonly occurs when young trees are moved from a protected situation, such as a shaded nursery, to an open garden site. Trees that have been shaded have thin and tender bark. If exposed to sudden intense sunlight, tree bark cells heat up rapidly. Since they are not adapted to very high temperatures, they are easily injured or killed. Sunscald may also occur on cold, clear winter days with sudden, intense sunlight. Recently pruned or transplanted trees are more susceptible to sunscald, as are young trees and species with smooth, thin bark. Sunscald may also occur on shade- loving plants, such as camellias, rhododendrons, dogwoods, and Japanese maple. Dry soil conditions intensify sunscald problems.
Bark turns dark brown, splits open, and dies. The splits form patches or long cracks, usually on the southwest side of the tree. The damaged bark and wood may be invaded by decay organisms, which enter the wood and cause cankers. Young trees may be killed. On shade-loving plants, sunscald causes leaf centers to turn a bronze color. Severely affected areas turn brown and die. Flower's may appear bleached.
Transplant in cool, overcast weather. Use burlap or tree-wrapping paper to wrap trunks and major branches of recently transplanted trees. Water immediately after transplanting, and thereafter water regularly, deep enough to reach tree roots, and fertilize to encourage new growth.