Bark splitting on trees and shrubs can be caused by several things. Physical damage such as extreme wind or damage from mishandling or rough treatment by people can stress and crack bark. Splits can also occur due to freezing temperatures. Water freezes in the stem over the winter during particularly cold nights. Bark splitting can also be caused by extreme heat, sunburn or even drought. Occasionally bark splits when trees grow too quickly often when they have been over-fertilized. Finally, diseases can damage the wood in trunks causing bark to split.

Plant recovery can happen on smaller bark splits. Trees 'seal' wounds by creating special wood around the damaged area of stems. This process can take years.

Trees with larger splits that go deeper into the wood of the stem or trunk could be a sign of structural failure. If you encounter bark splitting and/or wood cracking in the trunks of larger tree you should have the tree inspected by a qualified arborist.

If a stem crack is near the ground, the tree could have been wounded by something at the soil line. If the stem looks swollen, there could be a disease working in the stem. If a stem or bark crack is near the soil I recommend pulling back the mulch from the base of the plant. Sharp edges on wood mulch can damage thin bark and wound stems.

Being planted too deep can wound lower stems at the soil line. If planted as a field dug 'balled and burlap' tree, check to see if the landscaper removed the packaging. Make sure there is not string or other object girdling the stem.

So what can you do if you have a tree or shrub that has cracked bark? You should excavate the root collars, irrigate the plant during drought and fertilize twice each growing season. Monitor the larger wounds and call an arborist if tree failure is suspected.