Ortho GroundClear Weed & Grass Killer Refill, 1 gal. a fast-acting formula designed to eliminate weeds and unwanted grasses quickly, with visible results starting in just 15 minutes. This effective weed killer targets a wide range of common weeds such as chickweed, algae, dandelion, ragweed, shepherd's purse, moss, mustards, and oxalis, among others. It also controls various grasses including large crabgrass, annual bluegrass, wild onion, and perennial ryegrass. Suitable for use any time of the year, it works when applied to small, actively growing weeds that are 3 inches tall or wide. This versatile landscape weed control can be safely applied to walkways, driveways, landscape beds, and areas under trees. Once treated, weeds will change from green to brown within 1 to 2 hours, providing quick and effective results.