Common Issues in the Landscape: Included Bark
While the term “included bark” may not be familiar for those not professionally involved in the tree care industry, if you own trees or have seen any that failed after a storm, you have most likely seen the effects of this weakened area at the union of two or more stems/branches.
An eastern white pine that failed due to a weak attachment between the two co-dominate stems. Portland, Maine.
Included bark is characterized by the “V” shaped branch union where two limbs that are very tight together, are actually pushing against each other as they grow. In these situations there is bark in-between the two limbs rather than the proper wood fibers attaching one limb to the other as would be the case in a properly formed branch union. While not always visible there is also usually some amount of bulging around where the two sides meet, as well as possibly a seam or crack that passes below the point where the two limbs contact. Typically a proper union will have more a “U” shape with no seam or evidence of separation below the point of connection.
Colorado blue spruce
Northern red oak
The two photos above show two very different species of tree, both facing the same problems, included bark at the main stem attachment point. While some species of tree are more prone to this sort of growth, it is a possibility in any tree in this region.
These points below outline the progression of options depending on the severity of the issue:
The preferred approach is always pruning. If caught early enough, a qualified arborist will be able to structurally prune the tree to reduce or entirely avoid these issues in the future. This is why pruning of young trees is so invaluable.
If the issue has gone beyond the point of what pruning alone can correct, the next phase is a tree cable system. If installed correctly and with the proper hardware, these systems can be extremely effective in preserving a tree that might otherwise fail. If installed incorrectly, they can have catastrophic effects to the tree.
With any active splitting, the ANSI A300 Standard recommends through bolts at the union, in addition to the in canopy cable system.
In the worst of cases it may be deemed that the tree is too much of a risk and that it must be removed.
If you have trees with a similar look to the ones pictured above, it is strongly advised to take a proactive approach and contact your local certified arborist to have them assess the tree and form a plan to mitigate risk of failure. Unfortunately these issues will not correct themselves, but will only worsen with time as the tree becomes larger.
Installing a cable system in a large sugar maple with two co-dominate stems.