Crabgrass is actually considered more of a weed than a grass. It even looks a bit crablike--forming a flat mat that is reminiscent of the shell and scuttling claws of a crab. In lawns it begins to grow sooner than other weeds and can crowd out more desirable forms of grass. Crabgrass is highly adaptable. It can even be found sprouting from cracks in the sidewalk, where the dense spread of grass can hide the concrete itself. Mowing won't kill crabgrass. Instead, the grass flattens and continues to produce seed. Ridding yourself of crabgrass can prove quite challenging.
Rake your lawn with a lawn rake before mowing to deadhead crabgrass and prevent it from producing seeds.
Treat crabgrass with a selective herbicide. Selective herbicides formulated to kill crabgrass will not harm your lawn.
Remove the dead crabgrass clump with a V-shaped weeding tool. While it is alive, crabgrass releases chemicals into the soil that kill other plants around it. Once the crabgrass has been removed, your lawn will begin to recover.
Replant your lawn in the area where you removed the crabgrass. Replanting the lawn lessens the opportunity for crabgrass to return.
Treat your lawn with a pre-emergent weed killer in between growing seasons to prevent crabgrass seeds from sprouting the following year.