As the name implies, this symptom or damage is caused by exposure to the strong rays of the sun. It causes the bark to crack and cells to die resulting in the bark sloughing off exposing the wood beneath. This occurs at one of two times during the year.

  1. Summer Sunscald - Often summer scald will occur during times of drought or when the environment of the plant has been suddenly changed. This happens when a nearby tree that had been casting shade comes down during a storm or is cut. When this happens, the hot summer sun bears down on bark that was previously in the shade. This may cause the rapid loss of moisture from the affected area which may kill the cells in the bark.
     

  2. Winter Sunscald - This is also called Frost Crack or Southwest Crack since it often occurs on that side of the tree. Even in the depths of winter, the most intense sunlight comes from the southwestern horizon. On a very cold day, the bright sun may be enough to warm a small area of the bark on a tree. It will cause the cells to expand against the force of the frozen surrounding area. Something has to give so the bark will split under the stress. This is most common on young bark that is dark in color such as that on many maples. It rarely occurs on lighter colored bark or after the bark matures and forms thicker bark.

Treatment:

Unfortunately, once the bark has split, there is nothing to be done about it. Almost without exception a canker will form on the wound and will be there for the rest of the tree's life. It makes the tree a little less vigorous and hurts its aesthetics but many trees live for many, many decades with such wounds.

To prevent this injury, you can try to use a tree wrap on young trees until they develop

Trees Most Susceptible to Sunscald or Frost Crack

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

 

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