Legal Question in Real Estate Law in California

Probably not. While the tree is guilty of a trespass she has not altered the natural growth of nature. You have the legal right to cut the entruding branches but she likely does not have to pay for any of the cost. Image the neighbor's lot above you has a small stream running through it. Over the years, with less and less ground covering the area because of the construction of homes and roads, the stream has more water running through it, to the point that it now spills onto your lot causing mud to wash up to the foundation of your house. The neighbor could have done something to decrease the flow of water or its direction but did not. Who is economically responsible to clean up the mud on your property? You bear the entire costs.

I may not agree with Mr. Shers' analogy (the laws regarding naturally flowing surface water and those regarding trespassing tree limbs and roots are quite different), but I certainly agree with his conclusion. Trespass by tree limb or tree root is an unusual form of trespass, because the law allows the "victim" (you) to resort to self-help (trimming up to the property line). However, you have to do the trimming in a "non-negligent manner" (as one court decision put it, probably meaning in a way that doesn't kill the tree or make it likely to blow over in a storm) and you are not entitled to recover the cost of doing the trimming.