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Bark Split & Tree Trunk Cracks – What's Causing Them?
Bark Split & Tree Trunk Cracks – What's Causing Them?
I recently received a picture of a maple tree from one of our franchisees whose customer was asking about some cracks that were developing in the trunk. Nothing can take the place of seeing something in person, but I can usually provide a fairly good estimate of what is happening to a lawn or landscape plant from a picture.
Even after 35 years in lawn care, I am still learning new things. I was visiting one of our franchisees, Kent Fisher, in Green wood, IN. We were out looking at lawns and landscapes in his area, and he told me that a branch that projects perpendicular from the trunk has more structural integrity than one that parallels the main trunk, often forming a V-shape. I remembered that comment when I received the picture shown to the right. In this picture, you can see the scarring begins at the crotch of the tree and moves downward.
I cannot be 100% positive unless I was actually looking at the tree, but I am fairly sure that at some time in the past, this tree was pulled apart or twisted in a wind storm. The callus you see forming is the result of the tree repairing the damage caused by the environmental stress.
The stress crack may not have been visible to the homeowner, but the scarring shows that the cause was from an external force.
In the next picture, you can see cracks running vertical up and down the tree. Again, it is impossible to say what caused the cracks in the bark or when they occurred. However, there are several reasonable possibilities. In the spring, if it warms up enough for the tree to start moving fluid up the xylem and then it freezes, the fluid inside those tubes can expand and rupture the outer bark. Lightning strikes can also fracture the bark, but that damage is usually more pronounced and easier to identify. If the tree is growing quickly, the growth can also cause the bark to split. In this case, I feel the cause for the cracking was due to the tree growing quickly, faster than the bark could keep up with the growth of the tree.
As long as the heartwood, the dense inner part of a tree's trunk, is not showing through, there is nothing to worry about and the tree will be fine. If the heartwood is showing, than an easy access for wood decaying organisms has developed, which could lead to problems later on in the life of the tree. In this case, the crack that developed farther up is more of a concern than the lower bark splits. For either scenario, calling in a licensed arborist to assess the damage is the best plan. There are some things that are best left to tree care professionals.