KnockOut™ Weed & Grass Killer Super Concentrate is an all-purpose weed and grass killer which will kill almost all plants contacted. Spray carefully when air is calm to prevent spray or drift onto desirable plants, lawn grasses, shrubs or trees. Spray to evenly wet the weed. If necessary, use cardboard or plastic to shield desirable plants. If plants are accidentally sprayed, rinse off immediately with water.