How to deal with a neighbor's bad curb appeal
Check the rules
If a neighbor isn’t interested in a little friendly assistance — and he’s perfectly within his rights to refuse — you might choose to bring your local government’s code enforcement office into the picture.
Cities and sometimes even neighborhoods have rules about what homeowners can do with their homes and how they must maintain them (and the yard). There are often limits on how tall grass can grow, how far landscaping can hang over public sidewalks, what items are allowed in the yard, what color homes can be painted and much more.
Just be aware that getting the government involved can have unpleasant ramifications. Going around your neighbor "is only going to fuel the fire, and frankly, if you’re selling, you want friendly neighbors for all sorts of reasons," says relationship expert April Masini of AskApril.com.
But if going to your neighbor directly with your concerns has failed, getting the city involved can make sense.