Neighbors must care for growth on their property. I suggest you do two things: (1) check local ordinances to see if there are any that cover this situation and, if so, call the local official in charge to enforce the ordinance, and (2) if the growth has taken over your property line, write your neighbor, by certified mail, return receipt requested, informing them of the situation and giving them a reasonable time to correct it - if they refuse, your recourse may be self-help and billing them for the costs you incur.
