Ortho GroundClear 32 Oz. Concentrate Weed & Grass Killer is a fast-acting formula designed to eliminate weeds and unwanted grasses quickly, with visible results starting in just 15 minutes. This powerful weed killer effectively controls a variety of weeds including chickweed, algae, dandelion, ragweed, shepherd's purse, moss, mustards, oxalis, and more. It also targets grasses such as large crabgrass, annual bluegrass, wild onion, and perennial ryegrass. I for use any time of the year when weeds are small—up to 3 inches tall or wide—this product can be applied safely to walkways, driveways, landscape beds, and under trees. After application, weeds will change from green to brown within 1 to 2 hours, ensuring fast and reliable results.