By common intelligence and civic sense, a landowner is bound to maintain trees standing on his or her property so as to prevent injury to his or her neighbor’s property.  If the property owner in or adjacent to a developed area knows, or should know that a defect in one of his or her trees is an unreasonable danger to others outside the land, the property owner is bound to get rid of the danger.  Reasonable care and caution has to be exercised by a property owner by at least visually inspecting the trees and keep them safe and from causing any harm to others outside the property.

A tree that actually threatens physical injury to a person or property beyond the original boundary is considered as nuisance.  However, trees dropping leaves on the adjacent property is not a nuisance.

In Barker v. Brown, 236 Pa. Super. 75 (Pa. Super. Ct. 1975), a tree located in appellee’s yard fell into appellant’s yard causing damages.  An action was brought in by the appellant to recover damages upon which a summary judgment was passed in favor of appellee.  The decision was reversed on appeal and it was held that investing small amount of time and money was necessary to inspect and secure trees in a developed or residential area to prevent the increased danger and potential for damages represented by the fall of such a tree.  The court held that appellee was subject to liability for harm caused to appellant by a defect in the condition of the tree on appellee’s property.