Finding a split tree in your yard can raise all sorts of questions:
How did this happen?
Is it going to fall on my house?
Do I have to remove the entire tree?
These are all valid questions that deserve answers.
First of all, included bark is one of the leading culprits in tree splitting.
Although its name sounds friendly, its results are not. Included bark occurs when two bifurcating limbs grow closely together, in the shape of a narrow “V,” rather than the normal, healthy shape of a “U” or a “Y.” The fundamental difference between these shapes lies in the strength of the branch union. When two stems are crammed side by side (also known as co-dominant stems), bark begins to grow into the branch union. You might think that adding bark between two limbs would strengthen the connection, but in fact it has the opposite effect.
First, bark has no structural support. Think of it as the skin of the tree. The strength of your own body is determined by your skeletal and muscular systems—not by how much skin you have. If you want to increase your physical durability, you don’t go about adding extra folds of skin (most people are looking to lose these extra folds!).
Second, bark that grows into the branches actually places pressure on the juncture point. Bark is meant to grow on the outside of each limb, not the inside. Rather than binding the two stems together, the ingrown bark crowds out the more firm, sound wood that makes up the core of each branch. This ultimately weakens the branch union, making it more susceptible to forces such as wind damage. The wind creates an outward pressure that essentially pulls the weak areas of the tree apart until… you get the idea.
How can you prevent this?
While many homeowners inherit mature trees with co-dominant stems, there are ways to nip this problem in the bud in younger trees. Keep an eye out for limbs that seem packed together, or junctures where a small split is starting to form. Removing one of the limbs early on will enable the other one to grow normally, and will work wonders for the structure of your tree.
When in doubt, calling an arborist is your best bet. ISA Certified Arborists are trained to recognize early warning signs and develop solutions for mitigating existing risks. Sometimes this means removing a tree altogether, other times it means cabling limbs, and other times you can remove a single limb and save the tree.
The best thing you can do as a homeowner is to monitor your trees’ growth and catch included bark so you can exclude it as early as possible.