Whether you are liable for damages to your neighbor's property caused by the spreading roots of a tree on your property depends on what state you live in. In most situations, a neighbor who is bothered or worried by encroaching branches or roots of a healthy tree won't be able to successfully sue the tree owner. Instead, the neighbor can go ahead and trim the tree himself. In some states, however, neighbors may sue under certain conditions, including:
In many other states the law is unclear. In these states, a case might be successful if the tree:
In addition to finding out what the laws are in your state, there are lots of other questions for you to answer in getting to the roots of this dilemma. What's the cost of the damage to the neighbors' septic system? Do you like these neighbors and want to keep a good relationship? How about splitting the cost? If you love your tree, how about your having the roots cut back professionally so that the neighbors don't damage the tree if they exercise their right to trim back the roots to your property line?
Sometimes, no matter what the law dictates, it's better to spend money to fix a situation instead of paying the same money to a lawyer and losing a neighbor.