Crabgrass is a highly prolific, rapidly spreading weed. Although this annual plant is killed by the first hard frost, its seeds, which can number up to 20,000 seeds per square foot, lie dormant under the ground and reemerge the following spring. The plant grows via a process called tillering, by which it puts out horizontal branches near the base of the stem. The tillers grow along the ground, crowding out desirable plants. While it is most commonly found in lawns, crabgrass can also invade a vegetable garden.
Pull on some gardening gloves and prepare to get rid of as much crabgrass by hand as possible. Grab them at the base of the stem and pull upwards, taking care to remove the side shoots as well as the main body of the plant. Carefully place the weeds in a trash bag to limit the distribution of seeds. The best time to do this is before the weed flowers, in the early spring.
Cultivate the soil with a hoe or tiller. This will bury some of the remaining nodes and seeds too far below the surface for germination.
Treat the soil with a pre-emergent weed control product that contains the ingredient trifluralin, which is safe for use in a vegetable garden. This will get rid of the crabgrass by preventing its seeds left in the soil (and there will be some, as it is impossible to remove them all) from germinating for about two months.
Place a thick layer of mulch over the soil. This will block sunlight and also prevent the crabgrass from re-emerging.