Preen Lawn Crabgrass Preventer Use Before OR After the Weeds Come Up Preen Lawn Crabgrass Preventer prevents crabgrass and other grass and broadleaf weeds up to 4 months when applied prior to germination in lawns and ornamental turfgrasses. It also provides post emergence control of seedling crabgrass for up to 4 weeks after germination. Preen Lawn Crabgrass Preventer can be applied to the following turfgrasses when used as directed. Cool Season Turfgrasses Creeping Bentgrass Fine fescues Kentucky bluegrass Perennial ryegrass Tall fescue Warm Season Turfgrasses Bahiagrass Bermudagrass Buffalograss Carpetgrass Centipedegrass St. Augustinegrass Zoysiagrass Ingredients: Dimension Herbicide Safety: Keep people and pets off treated areas until dust has settled. Features Covers 5,000 square feet (17 lbs. bag) Controls new crabgrass up to 4 weeks after germination Stops growth of broadleaf weeds before they start Low Price Guarantee