A landowner has a duty to prevent nuisances which might adversely affect the property of an adjoining landowner. A nuisance is a substantial interference with the right to use and enjoy land, which may be intentional, negligent or ultra hazardous in origin, and must be a result of a defendant's activity. If a nuisance interferes with another person's quiet or peaceful or pleasant use of his/her property, it may be the basis for a lawsuit for damages and/or an injunction ordering the person or entity causing the nuisance to stop or limit the activity. Abatement of a nuisance may involve elimination of a nuisance by removal, repair, rehabilitation or demolition. Liability to an adjoining landowner for injuries resulting from the improper use of one's property has been founded upon the legal theory of nuisance.
The encroachment of a tree on the land of an adjoining landowner causing damage could be held to be a nuisance and result in damages against the landowner on which the tree was located. A landowner is generally held to the duty of common prudence in maintaining trees on his or her property in such a way as to prevent injury to his or her neighbor's property. Encroaching trees and plants may be regarded as a nuisance when they cause actual harm or pose an imminent danger of actual harm to adjoining property. In such a case, the owner of the tree may be held responsible for harm caused by it, and may also be required to cut back the encroaching branches or roots, assuming the encroaching vegetation constitutes a nuisance. Real damage must be shown to result from the encroaching tree and leaves.
Generally, however, in cases where trees belonging to one property owner fall on and damage or destroy adjacent property, the tree owner is only responsible for damage if some failure to maintain the tree contributed to the damage. If the damage was solely the result of a thunderstorm or act of God, the tree owner will not be responsible, as the damage could not have been foreseen. If a tree limb appeared precarious and the owner failed to maintain the tree after warnings, the owner may well be responsible for resulting damage when a storm causes the limb to fall. If, however, the tree was well maintained and a storm causes a tree limb to crash into a neighbor's roof, the tree owner is not responsible. If the tree owner allows the tree to grow so that it uproots the fence, it would be considered an encroachment onto the adjacent property. In that instance, the tree owner would be required to remove the offending tree. A boundary tree is one planted on the boundary line itself and should not be removed without mutual agreement. Leaves which fall off and end up on adjacent property are considered a natural occurrence and are the responsibility of the landowner on whose property they ultimately come to rest.
Property owners in every state have the right to cut off branches and roots that stray into their property, in most cases this is the only help that is provided by the law, even when damage from a tree is substantial. A property owner who finds a neighbor's tree encroaching must first warn or give notice to the tree owner prior to commencing work and give the tree owner the chance to correct the problem. If the tree owner does nothing, the tree can still be trimmed. As a general rule, a property owner who trims an encroaching tree belonging to a neighbor can trim only up to the boundary line and must obtain permission to enter the tree owner's property, unless the limbs threaten to cause imminent and grave harm. Additionally, the property owner cannot cut the entire tree down and cannot destroy the structural integrity or the cosmetic symmetry and appeal of a tree by improper trimming. Local laws should be consulted for applicable requirements in your area.