Crabgrass (Digitaria spp.) germinates in the spring when soil temperatures rise to 55 degrees Fahrenheit or above. It has flat, pale green blades and an aggressive nature that causes it to spread quickly throughout your lawn. Frost kills this annual weed, but its seeds can stay viable in the ground for up to three years. Reviving a crabgrass-filled lawn takes time and determination. Once your lawn is crabgrass-free, keep the weed from returning by maintaining a healthy lawn.
Wait until a day when the wind is calm to prevent spray drifts. Spray ready-to-use 2,4-D herbicide directly on the patches of crabgrass. Cover the blades of the weed thoroughly with the herbicide but not to the point of runoff. Follow the product's label instructions carefully. Reapply the ready-to-use weed killer in the same manner a week later on any spots you may have missed.
Wait three to four weeks after applying the weed killer before continuing. Water the dead patches of crabgrass with a garden hose until the area is soaked. Remove the dead crabgrass with a garden rake or dethatching rake until you are left with bare soil. Dispose of the dead grass in a trashcan or plastic bag.
Choose the grass seed you will use to revive your lawn. Warm-season grass grows best in hot climates and goes dormant in cool temperatures, turning brown. Cool-season grass works better for cooler climates and will turn brown in hotter temperatures. Consider planting grass seed that can handle your children and pets running and playing on the lawn. Kentucky bluegrass (Poa pratensis) -- a cool-season grass that grows in U.S. Department of Agriculture plant hardiness zones 3 through 9 -- and zoysia grass (Zoysia japonica) -- a warm-season grass growing in USDA zones 5 through 11 -- are two such species that have good wear tolerance.
Create trenches measuring about 1/4-inch deep in the bare soil with a flat shovel. Space the trenches about 2 inches apart.
Toss a handful of the chosen grass seed into the trenches. Moisten the soil lightly, using a garden hose set to mist. This setting stops you from accidentally washing the seeds away.
Keep the soil moist until the grass is established. Do not mow the new grass until it reaches about 3 1/2 to 4 inches high.