Here’s advice our researcher compiled, based on interviews with three experts:
Talk to your neighbors before hiring a tree company. Not only is it simple courtesy, it may make the job easier for your professional. One highly rated tree service provider told us that he's surprised at how many homeowners hire him to trim a tree belonging to a neighbor they've never talked to about the situation. That can lead to workers getting yelled at and even having the police called.
Make sure you know for sure who owns the tree. If the full trunk is in your neighbor's yard, the neighbor owns the tree, no matter how many branches or roots grow on your side of the property line. If the trunk rests on multiple properties, all owners must agree to trimming or removal.
Be sure you know your local laws, ordinances and restrictions. The bottom line in nearly every area is that any trimming efforts must not cause the tree permanent damage. Be aware that in many places, you're responsible for paying for damage caused if a neighbor's tree falls on your property. The case may be different if the neighbor's tree is dead. One expert suggests photographing neighbor's trees that seem to be dead and to make sure there's a record of complaints made to the property owner and, if nothing was done, to local officials.
Consult a certified arborist and, possibly, a real estate attorney. If you have any questions about tree ownership or the potential effects of trimming or cutting, it's best to get expert advice from a qualified professional.