Pruning a Tree That's Split at the Bottom

Addressing Split Tree Trunks

• Unfortunately, you cannot prune the split trunk itself. If the splitting is major -- for instance, half the tree has toppled over onto the ground, exposing the heartwood -- you are not going to be able to save that tree. It is best to simply have it removed rather than watch it die. However, if the splitting is minor, it may heal. Don’t try to prune out the damaged wood and do not coat the wound with sealant, which interrupts the tree’s own wound-healing abilities.

Pruning After Splitting

• If a tree’s split trunk is minor and you want to wait and see if it will recover, the best thing to do is to continue to prune normally. Generally this means pruning in the late dormant season, usually the end of winter or beginning of spring. Prune to remove diseased or damaged branches and foster a regular, eye-pleasing canopy. Thin branches to allow sunlight penetration by removing at a side branch or just outside the collar that attaches to the trunk.

Preventing Splits

• When you are pruning a tree, keep in mind that weak branches and co-dominant trunks are both recipes for tree splitting. Unless your tree is intended to grow as a multitrunked form, prune to a single central trunk, removing branches early in the tree’s life to provide the desired amount of clearance. Trunks and branches should have a strong crotch and grow upward, not out to the side. Prune multitrunked species so that all trunks grow upward rather than out, strongly attached to the base.

Pruning Correctly

• When pruning, remove branches that look weakly attached or do not grow upright. Use sharp tools so that you make clean cuts rather than mashing the wood. Disinfect your tools with rubbing alcohol before and after pruning, and when removing diseased limbs, disinfect between each cut. Although you can prune to address damage and disease at any time, wait until the end of the dormant season for maintenance pruning. Tree sealant is rarely, if ever, necessary, so avoid it unless a trained arborist has instructed you to use it for a specific reason.