Remove crabgrass as soon as you see it.
image by Ariel da Silva Parreira/sxc.hu
Crabgrass is a weed that needs sunlight to survive. If left alone, it will germinate quickly and spread throughout your lawn, using the water and nutrients that your grass needs, causing your grass to die. Removing crabgrass is, therefore, absolutely essential for a healthy, plush, green lawn.
Soak the area where crabgrass is located, if necessary. It's easier to pull out weeds that are rooted in moist soil. Let the water soak in before proceeding. You can also pull crabgrass after a good rain.
Pull out crabgrass as soon as you see it, and make sure you get its root. This can be successfully accomplished by grabbing the crabgrass as close to the ground as possible. Get a good grip and slowly pull the crabgrass out of the soil. Just tearing off the blades and leaving the roots will not remove the crabgrass.
Lightly mulch over the spot where the crabgrass was located. This will shade the ground, making it hard for any seeds or leftover roots that may be present to grow. Plant grass seed, if desired. Your grass will eventually spread to these areas, but planting grass seed will make the process faster. Keep the seeds well-watered for the first several weeks by watering in the early morning and evening, an inch or two of water at a time.
Use a chemical spray, if desired. Crabgrass-killer can possibly kill other nearby plants and grass. Follow manufacturer directions as each chemical spray is different with different potency. Apply in the early morning before it gets too hot and wear gloves when handling the chemicals.
Keep your grass mowed at about three inches tall. This will keep your grass thick and will help shade the ground so crabgrass cannot thrive. It is tempting to mow the grass short so you don't have to mow it as often, but this not only lends itself to more crabgrass, but to clover and dandelions as well.