If you have bare spots or thin areas on your lawn—which you likely will—you can overused those areas with the correct type of grass to thicken them.
Check with your County Cooperative Extension agent or your local garden center if you don’t know what type of grass you have. If appropriate, try some of the improved varieties that don’t need as much fertilizer and are naturally disease-resistant. Some types don’t even grow as fast.
In the North, the best time to overseed is in late summer and early fall, although you may also try this in early spring. Starting then gives the young grass plants a better chance to germinate, establish strong roots, and store food needed for a head-start in the spring. In the South, the recommended time to overseed is spring or early summer.
Before you begin, choose the seed that’s best for you, and consult with your nursery person about the correct amount for your site. Be sure to select one of the new varieties bred to withstand the stresses your lawn faces.
You have several tool options for spreading seed evenly and at the recommended rate. They include your own hands, handheld and walk-behind spreaders, and slit seeders, which are power machines that cut shallow slits in the soil and sow seed at the same time. Available to rent, slit seeders are the preferred tool, especially if you were not able to remove all thatch prior to overseeding.
If you will be spreading seed by hand or with a spreader, first use a thatching rake to roughen the exposed soil to a depth of 1/2 inch. Set the spreader to deliver the specific type of seed you have purchased. If you were not able to remove all thatch, sow a little extra seed. Similarly, the higher the percentage of weeds in your lawn, the more seed you should sow.
For sowing grass seed, the recommended approach is to apply seed to the edges of the area you are sowing first. Then divide your seed and apply half while walking in one direction, the other half while walking in a perpendicular direction. Spread extra seed on bare areas, lightly cover the seed with a mixture of compost and topsoil, and then spread more seed on top.
Finally, follow up by rolling all seeded areas with a water-weighted roller (available at a tool rental supply) that is one-third full to press the seed into the soil. This will help prevent the seed from drying out and consequently improve germination rates.
If you have a lawn with grass that spreads by stolons (aboveground runners), such as Bermuda grass, St. Augustine, zoysia, or buffalo grass, you may introduce new grass plants by inserting plugs rather than seed.