Crabgrass weeds grow quickly but can be thwarted with planning and patience. One way to get rid of crabgrass is to use a pre-emergent herbicide before the crabgrass can take hold. During the growing season, care for your lawn properly so it will develop strong, deep roots that will, in turn, choke out weeds.
Buy pre-emergent herbicide from your local gardening store. Purchase the correct herbicide for your type of grass and region (the store clerk can help you with this). Pay close attention to the last frost in spring. Apply the herbicide right after this frost, as this is the time when crabgrass begins to germinate.
Put on gloves before applying the herbicide, and read the instructions thoroughly on the herbicide. Using too much herbicide can harm the grass and you, but using too little will have no effect on the grass.
Apply the herbicide to your lawn. Directions don't vary too much on different brands; differences are usually found in the amount of applications or soil temperature. For example, the pre-emergent herbicide Sidurion must be applied to the lawn when the soil is about 50 degrees Fahrenheit.
Water thoroughly after the herbicide treatment for about 20 minutes. Saturate the grass enough so that the water gets below the roots.
Don't do anything to the lawn for two weeks, then reapply the herbicide again. Water generously afterward.
Watch your lawn to see if any crabgrass emerges. Pull any new crabgrass up at the base to remove the roots, then repeat the pre-emergent herbicide procedure. Water your lawn once a week so the grass roots can take a deep hold.