Ortho® GroundClear® Weed & Grass Killer Ready-to-Use 1 gal. 2-Pack. Acts on contact-see results in 15 minutes. Ortho GroundClear Weed & Grass Killer works on all types of weeds and grasses. OMRI listed for organic gardening. Rainproof in 2 hours (upon drying). Use on hardscapes, landscape beds, and around vegetable gardens (apply directly to weeds)