Crabgrass may be the only green thing that grows in some lawns, and as such should not be removed but treated as if it were royalty. But for those who have options and prefer soft, lush lawns, crabgrass can be a pesky problem and a frequently reoccurring one as well, if not removed properly.
It is important to keep the lawn at a uniform height throughout the entire growing season. It should be kept 2 to 3 inches tall to prevent the ideal conditions preferred by crabgrass. This type of grass won't form seeds until it is quite tall but if trimmed too low will spread even faster by reaching out in every direction along the ground. It sends out runners called stolons from the main plant, which then take root to create new crabgrass plants. This pattern of growth often resembles a multi-legged creature such as a spider or a crab.
Drought and Abundant Watering
To rid a lawn of crabgrass requires careful watering, allowing the lawn to go through short drought periods until the grass blades no longer pop back up when stepped on. At that time, a long soaking is required to perk the existing grass back up. The time required for existing grass to become drought-stressed varies from grass type to grass type but should be somewhere within one to two weeks. This will help to force the grass to put down deeper roots. Watering should begin when spring rains end and continue until the rains begin again in the fall. Because crabgrass prefers moist soil, don't water the lawn every day during the hot growing season. Grass that is watered every day or several times a week has shallow roots and is vulnerable to disease and invasion by weeds.
Removing Weeds and Re-seeding
If the lawn has only a few crabgrass plants, yank them out of the ground and burn them before they have a chance to go to seed, which happens during the late summer and early fall seasons. They cannot simply be pulled and left to die as they will put down roots wherever you happen to throw them. Add grass seed to any bare spots in the lawn after this is done. Do this preferably in the fall, after it begins to freeze during the night, as crabgrass tends to get a better footing in warm soil. Overseeding the entire lawn every few years can help as well by crowding out invading weeds.