Cracks in the Trunk, Sun Scald
Sunscald is a form of injury to the trunk of many landscape trees. Often called southwest injury, it usually occurs on the southwest side of young trees. As the sun shines on the tree trunk, cells within the tree break dormancy and become active. When the sun sets and temperatures get colder, the active cells are killed. This injury may appear as sunken and discolored bark. By spring, the bark may crack and fall off in areas along the trunk. Dead tissue is revealed under the cracked bark. The injury is most severe on thin-barked deciduous trees, such as honey locusts, fruit trees, ashes, oaks, maples, lindens, and willows. Sunscald occurs on warm winter days.
To prevent sunscald, the trunks of susceptible trees can be covered with tree wrap. This is put on in the fall and must be removed in March to prevent girdling and possible insect damage. Until the bark has thickened on young trees, they may need to be wrapped yearly. Be sure to scout for insects and carefully remove any bark not attached to the trunk of the tree.
Another product that can be used on the trunk is tree paint. White latex paint is often used in orchards to help prevent splitting and cracking on fruit trees. The paint will help reflect light and heat from the tree trunk. Due to aesthetic reasons, most homeowners are not interested in using tree paints. Both tree paints and wraps can be found at local garden centers and nurseries.
The last injury causing cracks is due to temperature fluctuations during the winter. These cracks are often called frost cracks. They are caused by expansion and contraction of a tree’s trunk. Kansas City is known for extreme temperature changes. As temperatures change quickly, bark from trees will crack. Frost cracks are not serious as long as they are kept clean to prevent disease and insects. Wrapping trees in the fall may help prevent further occurrence. Be sure to remove all wraps in the spring to prevent disease and insects from invading the tree.
Related Information: All About Pruning, www.oznet.ksu.edu