The autumn blaze maple (Acer x freemanii 'Jeffersred') is a hybrid of the silver maple (Acer saccharinum) and red maple (Acer rubrum). It is a popular medium- to large-sized deciduous tree whose leaves, as its name implies, turn bright shades of red and orange in the fall. When planted in the correct environment, the autumn blaze maple is a fast growing problem-free tree. However, bark splitting is a common problem with this species.
Damage to the trunk of any tree injures the underlying living tissue, causing it to die and split the bark of the trunk. Damage caused by mechanical means, such as with machinery or severe weather, are a common cause of splitting bark. Trees grown in lawn are susceptible to mechanical damage if the careless use of lawn mowers or string trimmers results in hard or continual collisions with the tree trunk.
Sunscald is a problem for newly planted trees or those with thin bark, like the autumn blaze maple. It occurs during the winter, when daytime temperatures become hottest in the afternoon and the sun is in the southwest sky. The trunk of the tree becomes heated, causing the living tissue to become active. As the sun sets, the temperatures may drop below freezing, which can kill the now active tissue and cause the bark to split. Sunscald is easy to identify since it occurs on the southwest portion of the trunk.
Healthy trees are naturally resistant to bark splitting. Autumn blaze maples prefer to grow in acidic soils that are kept consistently moist. If planted in less than ideal conditions, trees may be more susceptible to bark splitting and other problems. Remove grass from at least a three foot ring around any tree growing in a lawn to prevent contact with lawn mowers and string trimmers. Sunscald is easy to prevent by covering the trunks of susceptible trees in a light-colored wrap during the winter to reflect the sun's heat. Applying whitewash to trunks can also be effective.
Once the bark has split, there isn't much that you can do except to allow the tree to repair itself. Applying tar or other substance to the trunk only interferes with the tree's natural healing process. Water adequately and protect the tree during the winter. Over time, the autumn blaze will begin to heal and eventually cover the damaged area.