Anyone out there do cemetery lawn maintenance? If so, do you string trim around the tombstones or use a chemical application? I am maintaining 5 abandoned cemeteries (no new customers ;-)) and have to be very careful using a string trimmer around the old and often brittle tombstones. I would like to know if there is any chemical application that would be safe for the tombstones (won't discolor/stain or break down the stones themselves). Thanks!