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.
1 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.
2 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.
3 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.
4 Create trenches measuring about 1/4-inch deep in the bare soil with a flat shovel. Space the trenches about 2 inches apart.
5 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.
6 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.
Items you will need
- Ready-to-use herbicide containing 2,4-D
- Garden or dethatching rake
- Flat shovel
- Grass seed
- Wait until late summer to renovate your lawn if possible. According to the University of Massachusetts-Amherst Agriculture and Landscape Program, mid-August to mid-September is the ideal time to renovate your lawn, thanks to cooler temperatures and adequate rainfall.
- Wear protective clothing -- safety glasses and rubber gloves -- when working with herbicides.
- Follow the directions and waiting period for reseeding as listed on the herbicide label.
- Keep children and pets away from the area until the herbicide dries completely.
- Pregnant and nursing women shouldn’t use 2,4-D herbicide. According to the Wisconsin Department of Health Services, it is not known whether 2,4-D is safe to use during pregnancy, but evidence has shown that high levels of 2,4-D exposure increases the risk of birth defects.
- Flush the area with cool water for several minutes if herbicide comes in contact with your skin or eyes.
- Contact poison control immediately if the herbicide is swallowed.
- University of California Statewide Integrated Pest Management Program: Crabgrass
- University of Massachusetts Amherst Agriculture & Landscape Program: Lawn Renovation & Overseeding
- The Family Handyman: How to Get Rid of Crabgrass
- University of Georgia College of Agricultural and Environmental Sciences: Weed Control in Home Lawns
- Spectracide: Weed Stop for Lawns Plus Crabgrass Killer Label
- National Gardening Association: Poa Pratensis
- Missouri Botanical Garden: Zoysia Japonica "Compadre"
- Wisconsin Department of Health Services: 2,4-D