I remember of two fellows that had a similar situation, property line and trees.
the one with no trees had a backhoe come in a dig a ditch about 4 ft from the fence line on his side of the line.
of course the open ditch about 6 ft deep killed the trees along the fence. but that is a lot of hassle and could cause other problems.
good fences and well marked property lines, normally make for good neighbors,
as dad always said:
take care of your stuff and if you have to borrow something twice, you need to go buy one for yourself.