First, who owns a tree on a property line?
Under the common law, an invisible barrier starting at the center of the earth and extending to the stars runs along a real property boundary delineating each owner’s property. Today, that ownership interest is subject to claims about mineral rights underground and the rights of flight overhead.
A boundary tree is a tree whose trunk, roots, or branches break through the invisible barrier extending onto the property or air space of an adjoining owner.
In most jurisdictions, each landowner has a tenants-in-common ownership interest in the boundary tree. Each common owner of the tree may lawfully trim vegetation overhanging or roots undercutting their property, but not in a manner that will kill the tree.
Most courts have stated a landowner does not have legal authority to completely cut down a boundary tree. Like other tenants-in-common ownership interests, each owner is entitled to use, maintain, and possess the boundary tree, but not in a manner that interferes with the co-equal rights of the other co-tenants.
Therefore, each landowner can trim the branches or cut back the roots, but not so much that the ownership rights of the neighboring owner in the tree are put in peril by causing the tree’s death.