Principles of Pruning, Part 3: Included Bark

Pruning is an important part of tree care, and to keep a tree healthy and growing, knowing the proper techniques on how to prune is different situations is essential to being a responsible tree owner.

If pruning is not done regularly and started when the tree is young, situations could arise that could hinder the growth of the tree, like included bark. This is often caused by a co-dominant stem, or a competing leader.

“A co-dominant stem itself isn’t horrible,” said Dr. Jeff Iles, chair of the Department of Horticulture at Iowa State University. “But with that comes included bark.”

Included bark is when the bark has turned into itself, and creates a situation where the tree could give way or split down the middle, causing problems with the tree and a safety hazard for humans.

“It is much easier to take care of those things when the plant is young, then when the tree gets older,” Iles said. “To walk away and do nothing might be inviting disaster for a tree.”

Iles said that it is important to not take too much tissue off of a tree at one time, and a process that could be taken is to prune off parts of one of the competing leaders and remove the rest at a later time.

One thing to keep in mind with included bark is that the cut likely has to come from the outside, with hope that it meets in the middle, which can be difficult sometimes. Iles said that trees should not be pruned more than 15% to 20% at one time.

He said that he often gets asked about what to do after the prune, and if the wound on the tree needs care.

“Current research tells us that we really don’t need things like pruning paints,” Iles said. “It might make us feel better, but it really doesn’t do much for the tree.”

He said the one exception to that might be if pruning an oak tree during the growing season, but that is not recommended. This could cause oak wilt, which is a disease that can kill an oak tree.  

For Part 1 of this series click here.

For Part 2 of this series, click here.


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