Weed B Gon MAX Plus Crabgrass Control kills lawn weeds, right down to the root. But here's what makes Ortho Weed B Gon MAX Plus Crabgrass Control so cool: it's tough on weeds, but won't harm your lawn when used as directed, so you can use it on your lawn when weeds or crabgrass pop up. It's rainproof in one hour, and it starts working overnight.