The best time for lawn renovation throughout the U.S. is mid-August to mid-September. Most weeds have not yet dropped their seeds and there will be little new weed growth. Also, reseeding at this time will give the new grass a chance to establish itself before going dormant for winter. Get rid of the weeds by manually pulling up large, spreading weeds. Follow up by applying a selective herbicide product that kills common broadleaf lawn weeds while not harming grass. For tough grassy weeds, like quack grass or crabgrass, use a nonselective herbicide such as glyphosate on the spots where these weeds have established themselves. Normally, all weeds will be dead within two weeks. Apply another herbicide dose in three weeks to get newly sprouted weeds.
If you have had a dry summer with below-normal rainfall, you need to replenish soil moisture before preparing a seedbed. Give the entire lawn a thorough watering, soaking until water has penetrated to a depth of at least 6 inches, then allow the surface to dry for a day or two before starting soil preparation.
Kill the Weeds
The soil nutrients most important to healthy grass plants are nitrogen, potassium and phosphorous. Supply these nutrients by applying a commercial fertilizer formulated for starting lawns and lightly rake it into the soil before you reseed. Buy a grass-seed blend suited to your climate and local conditions and spread it over the lawn with a drop spreader or rotary spreader. Absent a different recommendation from the grass-seed grower, spread the seed at a rate of 2 pounds per 1,000 square feet on a lawn with substantial plots of live grass and 3 pounds per 1,000 square feet on bare soil. Water lightly once or twice a day to keep soil moist but not sopping wet. Don’t mow until the new grass gets 3.5 inches tall.
Most deteriorated lawns have a built-up layer of dead and partially rotted grass stems, roots and rhizomes just below the green grass leaves. This is known as thatch, and it must be removed before reseeding so water and fertilizer can reach the new seed. For small lawns, you can remove thatch with a garden rake. For large areas, go over the lawn with a power dethatcher, also known as a vertical mower or power rake. These machines can be rented from garden centers. Remove the clumps of matter left by the machine with a garden rake and level the soil by raking it.
If you are faced with a neglected lawn that’s partially dead and is being taken over by weeds, you may be able to renovate it. Restoring a deteriorated lawn may be possible if the weeds and dead spots cover less than 40 percent of the lawn area. Renovation of a weedy lawn involves more than just mowing down the weeds and throwing some grass seed over the lawn.
Remove the weeds from the area by either manually pulling them out of the ground or applying weed killer to the area. Hand-pulling weeds is safer for the soil, but removing all the roots can be difficult. Chemical weed killer kills the weeds and their roots, but may damage grass seed and leave pesticide residue in the soil, if you plant the seeds too soon after the herbicide application. If you choose to use weed killer, wait 2 to 3 weeks before planting new grass seed.
Till the top 6 inches of soil with a soil tiller. You can rent or purchase soil tillers at home improvement centers and rental yards. After the tiller turns under the dead weeds and soil, rake the soil with a garden rake to level the area as much as possible. Remove large rocks and break up clumps of soil.
Apply a thin layer – about 1/4 inch – of high-quality topsoil over the grass seed. Applying too thick and the seeds have a hard time germinating. Attach a garden hose sprayer with a mist option to a water hose. Dampen the top 6 inches of the soil with the water hose set on mist. Using a mist of water instead of a stream will prevent the seeds from washing away.
Cover the soil with the correct grass seed for your location and the amount needed to cover the area. For example, some parts of the San Francisco Bay area work best with warm-season grasses — such as St. Augustine, buffalo or zoysia grass — while other Bay areas thrive with cool-season grasses such as tall fescue and perennial rye. Use your gloved hands to distribute the seeds evenly over areas smaller than 150 square feet. For larger areas, use a seed spreader.
Trying to grow grass in a weeded area is a frustrating task that generally provides undesirable results. Weeds are aggressive and invasive plants that choke out grass and flowers. They quickly take over an area and are notoriously hard to get rid of. When you choose to grow grass in an area overrun by weeds, you essentially have to start fresh by establishing new turf.
Aeration improves your grassroots’ access to air, nutrients, and water. Use a spike or core aerator to break up the soil. If you use a core aerator, be sure to make two to three passes in different directions. Allow the plugs of soil you remove to decompose on top of your soil layer rather than remove them.
Now, you can apply your soil amendment to ready your soil for the grass seed or sod.
Step 3: Apply the Treatment
First, you need to choose the right type of seed for your lawn. That will depend on the region you live in—one that needs cool-season grasses, warm-season grasses, or a transition zone that allows more flexibility. After you determine which category you need, you can select specific grasses that may have attributes you’re after, like heat- or drought-resistance.
Once the weeds—and grass, if applicable—turn brown, it’s time to bust out your rake. Rake up as much of the weeds as you can. Use your tilling fork to pull any extra weeds out and till the soil to prepare it for your amendments and seed.
If your lawn is patchy and full of weeds, it will never be the envy of the neighborhood. What you’re after is a lush, green lawn with even grass and no dandelions poking their way through. That may sound hard to achieve, but it isn’t too difficult if you follow these steps.