Is a property owner obligated to trim trees that hang onto my property?
Adjoining landowners can find themselves in disputes over fences, overhanging branches and party walls. Boundaries are frequently marked by partition fences, ditches, hedges, trees, etc. If the tree trunk is located wholly on one property, the tree is "owned" by that property owner. Even if the branches go over the property line. If the trunk straddles the property line, you have a shared tree. A tree growing in the boundary line is the joint property of both owners of the land.
There is no clear legal rule regarding trees that grow on the boundary between two properties. In some jurisdictions, trees standing along a boundary line are the common property of the neighbors on either side of the boundary. The general common-law rule is that one cannot complain of trees or shrubbery on adjoining land regardless of their thickness or height, since the adjoining landowner is within his or her rights in making such use of his or her land.
Although you may cut tree limbs and remove roots from your neighbor's tree where they cross over the property line, you cannot do so if it will damage the continued viability of his tree. The neighbor with the branches reaching onto his or her yard has the right to trim those branches back to the property line (and pay for it himself or herself). The neighbor cannot demand that the tree owner pay to trim the branches. The neighbor cannot harm the tree, kill it, or chop it down. If the neighbor harms the tree, he or she could be liable for damages.
Your neighbor can be held liable only if his failure to maintain the tree in some way contributed to the damage. If the damage was merely the result of a large storm or an act of God, the neighbor will not be liable for the damage, because the damage could not have been foreseen. If a tree limb appeared precarious and the owner failed to maintain the tree after warnings, he is responsible for resulting damage when a storm causes the limb to fall. If the tree was well maintained and a storm knocked it down onto your roof, the neighbor is not responsible.
Trees may be considered an encroachment. For example, when Neighbor A's tree is alllowed to grow onto the Neighbor B's property and damage a fence, it is an encroachment on neighbor B's property. Neighbor A may be required to remove the tree. A Court has discretion to balance hardships and deny removal of an encroachment if it was innocently made, the cost of removal greatly exceeds the inconvenience to plaintiff, and the plaintiff is compensated for damages caused by the encroachment.