When your lawn contains more weeds than grass, it's time for a complete overhaul. Spraying an herbicide that controls broadleaved weeds and crabgrass (Digitaria spp.) takes care of the weed problem, but bringing the lawn back to a healthy condition requires reseeding and providing aftercare.
Choosing Herbicide for a Lawn
Selective herbicides that target weeds but leave turfgrass unharmed are best for lawns. A ready-to-use herbicide that is 4.85 percent 2,4-D, dimethylamine salt, 1.61 percent quinclorac and 0.45 percent dicamba controls crabgrass and broadleaved weeds in most lawns, but check the product's label because some lawn herbicides damage certain types of grass.
- Spray the herbicide when weeds and grass are actively growing. If the lawn is dry, irrigate it one or two days before applying the herbicide.
- On a windless, dry day when temperatures are below 90 degrees Fahrenheit, or below 85 F for a bermudagrass lawn (Cynodon spp.), evenly spray the herbicide over the grass.
- Avoid spraying flowerbeds, shrubs, trees and other vegetation.
- Spray the herbicide again after two weeks if some weeds are still growing, but don't apply the product more than twice per year.
Reseeding Bare Patches
Reseeding a lawn with the same grass type as the existing lawn grass avoids visual differences between new and established turf. In warm climates, bermudagrass is common. A vigorous, spreading grass, bermudagrass is hardy in U.S. Department of Agriculture plant hardiness zones 7 through 10. A cool climate lawn might contain tall fescue (Festuca arundinacea), which is hardy in USDA zones 4 through 7, or a similar grass.
How to Reseed
- Rake the bare patches until the soil is level and crumbly.
- Sprinkle the grass seed over the bare patches first from side to side and then up and down to provide even coverage. The seeds should lie about 1/4 inch apart.
- Gently rake the soil to cover the seeds about 1/8 inch deep.
- Fit a soft-spray attachment on a garden hose or a fine rose attachment on a watering can, and water the patches until the soil is moist to a depth of 4 inches.
- Water the patches each time the soil surface is dry.
Fertilizing the Lawn
Fertilizing on a regular basis provides a long-term fix after renovating a weedy lawn. Fertilizing helps grass grow strongly and outcompete weeds, but the correct amount of fertilizer to apply depends on the grass type and the fertility of the soil. If, for example, a soil test result isn't available, then bermudagrass should be fertilized at a rate of 2 to 4 pounds of actual nitrogen per year, and tall fescue should receive 3 to 6 pounds per year. Divide the total amounts into four portions, and apply one portion four evenly spaced times per year when the grass is actively growing. Water the lawn after applying fertilizer.
Watering the Grass
Drought stresses lawn grass and allows weeds to take over the space. Watering infrequently but deeply encourages the best grass growth. Water an established lawn when its soil is dry to a depth of 1 to 2 inches, and apply enough water to moisten the soil 6 to 8 inches deep. A lawn rarely needs water in cool or cold seasons, when grass grows very slowly or stops growing.