Keep crabgrass out of your lawn.
image by Makio Kusahara: sxc.hu
Crabgrass is not grass at all. It is a weed that if left on its own, will take over your lawn. It grows quickly and will use up all the water and nutrients, leaving little for your nice plush grass. Eventually, your grass will die and all that is left is crabgrass. Fortunately, you can kill crabgrass before this happens.
Purchase a chemical spray that is labeled specifically for getting rid of crabgrass. Read the label to be sure it is safe for the kind of grass you have. For example, Centipede and St. Augustine grasses might be damaged or killed by highly concentrated chemical sprays, so check the label first.
Prepare to use the crabgrass killer as soon as you see the first signs of crabgrass. You do not want the crabgrass to spread, which is then more difficult to remove.
Mix the crabgrass killer with a spreader sticker. Example brand names include Hi Yield and Lesco. Using a spreader sticker will help spread the chemicals evenly over the grass and help it stick. Use about 1 oz. per gallon of crabgrass killer. Read the label carefully for exact dosing amounts.
Apply the crabgrass killer in the morning, before the heat of the day. Do not cut your grass first. You can spot treat your lawn if the crabgrass is only in a few spots, or apply it to your entire lawn if the crabgrass has spread.
Reapply every two weeks, as necessary. It should take only two or three applications to get rid of your crabgrass.