Legal Question in Real Estate Law in California

Probably. First, if the tree branches were contacting the neighbor's building, either constantly or when the wind blew, that would be a trespass to their property. Second, although the usual remedy for trespass is to go to court and get a court order, California case law allows self-help for trespass by tree limbs or tree roots. The scope of the allowable self-help is that the offended neighbor may trim the branches or roots to the property line, but it must be done in a non-negligent manner, i.e., without killing the tree or making it likely to fall over in a storm. The neighbor doing the trimming cannot re-collect the cost of the trimming work from the tree owner when it is done under the self-help rule. Lastly, California and most other states also observe a principle with respect to zero-lot-line buildings that the owner has an implied easement, of somewhat limited scope, to enter the adjoining property to do maintenance and inspection of their own property.

I would add that I could not find a California case or discussion in a treatise that was exactly on point, so my answer is qualified with "probably" and is cobbled together with analogies and reliance on similar situations. Finally, if this is a condominium or some other kind of planned development with CC&Rs;and rules of its own, these should be reviewed for anything that requires a different conclusion.

Your post is confusing. If the wall sits on your property, it is not their wall, it is your wall. It is also not clear where the lemon tree is. If the tree stands on your property, it is your tree. The neighbor has the right to prune the branches back to the property line, but does not have a privilege to come onto your property and cut the tree or prune it there. That is trespass.