In the simplest terms, overseeding is adding grass seed to your existing lawn without turning the soil. This  adds more color to your lawn, helps create thicker grass, and introduces enhanced varieties of grass to your lawn.

Lawn overseeding is a great option for homeowners whose lawns have suffered from drought stress, insect or disease damage, or that show other signs of decline such as thin sparse grass, bare patches or lack of color.
Overseeding your lawn with newer, improved types of turfgrass is often the best way to thicken the lawn, and improve its health and appearance. The newer turfgrass varieties are better able to resist damage from drought, diseases and lawn damaging insects.

Read more about the benefits of overseeding at Benefits Of Overseeding A Lawn

The best time to overseed your lawn depends on where you live. In the cooler northern climates, the best time to overseed is in late summer to early fall. In fall the soil is warm enough to support germination, but the temperatures aren’t too extreme for the tender new grass to develop before winter sets in. Soil moisture needed for germination is more favorable as well.  Spring is an alternate time if not completed in fall, but do as early as possible to allow seedlings enough time to establish before summer heat begins.

Seed germination and establishment requires good contact of seed with soil. Inspect your lawn for presence of thatch.  If too thick, its best to aerate your lawn before overseeding or if filling in patches remove the thatch and dead grass before spreading seed in bare areas of your lawn. To prepare your lawn for overseeding, cut the grass short, using the lowest setting on your mower. Don’t forget to reset the blades to a higher setting after the overseeding is complete and resume a normal mowing height as you typically don’t want to cut the grass this short. If cutting your lawn short before overseeding, bag the clippings. While you might normally leave them to help feed the lawn, you want to remove the clippings so that the grass seed can make good seed:soil contact for faster germination. After mowing, rake your lawn to remove any remaining debris and thatch, and to loosen the top layer of soil.

When choosing seed, be sure to select the right seed for your region of the country and for your yard conditions, and follow the package directions on your chosen grass seed. Use a seed spreader to make the job faster and ensure that the seed is spread evenly. If your soil is especially compacted, you may wish to aerate the lawn before you overseed. Keep in mind, though, that if you aerate before overseeding, you need to choose a type of grass seed that spreads easily, such as bluegrass. Otherwise, the seed is likely to get caught in the aeration holes, creating a patchy or clumpy lawn.

Watering is one of the most important aspects of successful overseeding. You need to water the seeds into your lawn immediately after spreading, and continue to water daily until the seeds germinate, which can take up to two weeks. The first watering should be a heavy watering (about an inch of water). After that, your watering can be lighter.  Once the grass has germinated, be sure to water every few days  giving the grass a good deep soaking. When the grass is fully established and the same height as the existing lawn, water it according to the instructions for that type of grass. While the new grass is getting established, try to limit activity on the lawn and avoid mowing as long as possible. Once the grass is the same height as the existing lawn, you can continue to mow as you normally would.

Most homeowners only need a lawn mower, rake, and seed spreader to overseed the lawn. In some cases, you may need to invest in an aerator or have your lawn aerated by a professional lawn care company beforehand, but otherwise, simple tools are all that are needed.

There are some benefits to hiring a professional lawn service  A professional lawn care company can help you make sure that overseeding is something your lawn actually needs.  Since patchy, scraggly lawns can be caused by other problems, you could be wasting your time and money on overseeding. A professional lawn care service can thoroughly evaluate your lawn   and come up with a more complete plan to get your lawn green and healthy.

Professional lawn service also have more advanced equipment than most homeowners. Tools like de-thatchers, power rakes, and slit seeders get the job done quickly, accurately, and more effectively than you can with a rake and a seed spreader. Ensuring that the job is done right the first time is often well worth the investment.

Regardless of your approach, overseeding is an easy and effective way to give your lawn a boost and help it  look great for years to come.