Crabgrass (Digitaria spp.) is a vigorous, warm-season annual that spreads during the summer and competes with desirable grass for soil moisture and nutrients. Left unchecked, the aggressive weed can take over a beautiful lawn within weeks. Although chemical methods effectively kill crabgrass, adopt a natural or organic method of permanently eradicating the weed from your lawn. Also follow a proper maintenance schedule so your grass is healthy and resists competition.
Things You'll Need
Corn gluten meal
If the infestation is small, put on gardening gloves and pull out the crabgrass by hand. Make sure you pull out the roots to prevent the weed from regrowing. Moisten the soil lightly until it is workable, and loosen the soil around each crabgrass plant so it slides out easily, along with its root system. Collect the plants into a tarp and discard.
Pour boiling water over the crabgrass to burn it. Boil water in a long-spouted kettle and immediately pour it over the plant. Wear closed-toe shoes and long pants to prevent accidental drips and splashes.
Spray or douse a crabgrass infestation with an organic weed killer such as vinegar. For best results, use vinegar that contains 20 percent acetic acid. Spray the vinegar over targeted plants or pour it over large infestations. Apply the vinegar during midday, when the sun is at its strongest, to speed up the burning process.
Mulch mature crabgrass using wood chips, landscape fabrics or compost. Spread 3 to 6 inches of coarse mulch or 2 to 3 inches of fine mulch over the crabgrass plants. Replenish the mulch frequently to maintain its depth.
Solarize crabgrass during uninterrupted periods of strong sunlight using plastic. Mow the plants as short as possible, and spread a black plastic sheet over the area. Place bricks over the edges of the plastic sheet to weigh it down and keep it in place. Crabgrass dies in four to six weeks.
Rake the lawn so the seed branches of the crabgrass stand upright, preferably above the grass. Mow the lawn immediately, collecting clippings in the collection bag. Continue to mow frequently to prevent the seeds of existing crabgrass from spreading and germinating. Continual mowing also reduces the structure of the plant, causing it eventually to die.
Irrigate the grass infrequently but deeply to weaken existing crabgrass. Frequent, light irrigation promotes shallow roots and encourages the noxious weed. Wet the soil 6 to 8 inches deep, and do not water until the top 2 inches of the soil become dry.
Apply corn gluten meal over the grass in early spring, before crabgrass germinates. Spread 10 lbs. of pellets per 500 square feet, and water lightly. The organic material prevents the seeds from germinating, thus keeping the noxious weed from spreading.
- National Gardening Association; Crabgrass; Barbara Pleasant
- All About Lawns; 10 Steps to Becoming Crabgrass Free; Alex Russel; Aug. 22, 2006
- Turfgrass Science; Control of Crabgrass in Home Lawns; Zac Reicher, et al.; May 2006
- UC IPM Online; Crabgrass; R.H. Molinar, et al.; June 2010
- University of Illinois Extension: Managing Crabgrass in Home Lawns