Crabgrass, sometimes known as finger grass or crowfoot grass, is a common weed in many North American lawns. The weed's hardy nature and prolific seed production helps it spread quickly. Without proper management, crabgrass can overwhelm your lawn and choke out your grass. Take steps to kill crabgrass in a lawn-safe manner to preserve your grass' health and appearance.
Prevent crabgrass. A lush and densely grown lawn will keep crabgrass from invading. Mow at a minimum height of 2 4/10 inches to avoid exposing soil. Water deeply, as light watering creates a crabgrass-friendly environment. Space watering so that your next watering session occurs when the grass begins to turn bluish due to drought stress. Also, fertilize twice annually using a standard lawn fertilizer.
Remove crabgrass manually. This option works best for minor crabgrass populations and spot-removal. Use a garden fork or spade to dig out the crabgrass bunch. Grasp the weed at its base and pull away from the soil. Lay the crabgrass in the sun to kill it.
Use pre-emergence herbicides. These chemicals prevent crabgrass seeds from sprouting, breaking its life cycle. They do not affect already-growing plants, thereby protecting your lawn. Example products include Oxadiazon and Benefin, and are available at most garden stores and nurseries. Sprinkle onto your lawn according to the manufacturer's guidelines as toxicity varies by product, then water your lawn thoroughly to distribute the chemical into the soil.
Apply post-emergence crabgrass herbicides. These herbicides kill the crabgrass and will completely eradicate any crabgrass populations when used in conjunction with a pre-emergency herbicide. Example herbicides include Fenoxaprop and Dithiopyr, and target crabgrass without harming lawn grass species. Spray onto your lawn, misting all exposed surfaces according to the manufacturer's specifications. Avoid watering or mowing your lawn for 24 hours after applying the product.