“So, my mother owns a house, and she had a new neighbor move in next door. He asked her if he could build a gated fence across her property for some reason, and she said “No”, so he cut part of her tree down (part was hanging into his yard, but he cut down past the property line). He came onto her property the other day and weed wacked one of her gardens and then said “I hope you didn’t mind.” Several occasions like this have taken place, and every time, she makes sure that he understands their property boundary and states that she does not want him to cross (he mows every week over her vines ON HER PROPERTY and is constantly leaving tools on her property on top of her plants). She doesn’t want to escalate the situation by being mean, but it very obviously is annoying her. Legally, what can she do?”

Build a fence.

Legally, she could sue her neighbor for trespassing, for damage to her property (trees, plants, etc.), for nuisance (leaving tools, etc. on her land), and probably some other things I’m not thinking of. But if she doesn’t want to “escalate” things, she probably doesn’t want to do any of this. Building a fence isn’t so antagonizing, but makes it unlikely that the neighbor will “accidentally” do things on the wrong side of the property line.