Root out the toughest weeds and grasses with Roundup Dual Action Weed & Grass Killer Plus 4 Month Preventer Concentrate. This formula kills existing weeds and grass down to the root, and prevents new weeds from growing for up to 4 months by creating an invisible barrier in the soil. Apply only where you want to kill existing weeds AND prevent future weed growth for up to 4 months, such as cracks and crevices in driveways, sidewalks, and patios, along fences, in mulched beds or around the base of well-established desirable plants, shrubs, or trees, and on gravel areas. In order to prevent new weeds and grasses from growing, you must spray the entire area you want to control, not just the emerged weeds. For best results, apply during warm, sunny weather above 60°F. Rain or watering 30 minutes after application will NOT wash away effectiveness. After application, weeds will begin to yellow and wilt within hours with complete kill in 1 to 2 weeks. All ornamental bedding plants (annuals and perennials), trees, shrubs, sod and seed can be planted 4 months after application. Roundup Dual Action Concentrate covers up to 1,600 sq. ft.