Crabgrass is an invasive grass species that forms large clumps that spread aggressively and can be especially troublesome in lawns. Homeowners have several control options, both physical and chemical, to eradicate crabgrass from their lawn and garden. Whichever option you use, implement it sooner rather than later. It's easier to remove isolated crabgrass patches than it is to get rid of large patches that have already scattered seeds.
Remove the crabgrass manually if it's an isolated problem. Grasp the grass clump in one hand while sliding a hand-held spade under the clump at an angle. Pull upwards to uproot the crabgrass. Make sure you've removed all of the underground runners, as failure to remove these will result in new crabgrass clumps appearing.
Apply a granular pre-emergent lawn herbicide, such as prodiamine, pendimethalin or benefin, to your lawn in March or April. This prevents any crabgrass seeds in your lawn from germinating. Apply according to the labeled guidelines--herbicide toxicity varies widely by brand and product--and follow the application with a short watering session that moistens the soil to a depth of 1/2 to 1 inch. This carries the herbicide down to the root level where the crabgrass seeds may lie.
Treat your lawn with a post-emergent herbicide if it's late in the growing season and crabgrass is already present. Use an herbicide based on a chemical such as monosodium methanearsonate that's formulated to target broadleaf weeds but not harm turf grass. Apply according to the product's label.
Get rid of crabgrass in your ornamental flower beds or vegetable garden. Pour boiling water, which collapses plant cells, directly on the grass clump once a day until the plant dies. Alternatively, spray the plant with a glyphosate-based herbicide, being careful not to get the herbicide on any desirable vegetation.