I had a customer request a pre-emergent type weed preventer for his rock beds on the side of his store. No big deal, except he said that he heard that there was some type of chemical that would keep absolutely all weeds from coming up for an entire year. He only wants this one type of preventer, but doesn't know what it is called Does anyone know what he is talking about or any suggestions on what to get. I use Lesco as my fert / chem supplier. Thank you.