Weed control for sensitive areas of your landscape, such as warm season established lawns and ornamental landscapes. Use Hi-Yield Turf & Ornamental Weed & Grass Stopper to control crabgrass and other broadleaf weeds for up to 4 months after application. This weed killer works best when applied before most weeds emerge, but it will help control crabgrass for up to 4 weeks after germination.