Frost Crack on Crab Trees
The most common reason for cracks and splits on tree trunks is cold temperatures. Frost cracks are caused when the inner and outer wood in the tree's trunk expands and contracts at different rates when temperatures change. This happens when winter temperatures plummet below zero, especially after a sunny day when a tree's trunk has been warmed by the sun.
Prevention: Frost cracks are not preventable. Frost cracks often close during summer only to reopen in succeeding winters. They do not seriously hurt trees although they provide openings where certain disease organisms may enter, particularly if the tree is in a weakened condition.
Wrapping tree wrap paper around the tree in the fall may help. Be sure and remove it each spring so insects do not work themselves into the wrap area. Do this for one or two seasons until the bark begins to roughen. Tree trunks can also be treated with white latex paint.
Another form of cracking is Sun Scald. Sun Scald occurs in the winter usually on the south or west side of the trunks and branches. The damage takes place when the cells in the living tissue beneath the bark break dormancy on warm, sunny days and then rupture and die when night temperatures drop below freezing at night.