Homeowners overseed an existing lawn for two main reasons: To thicken and improve the appearance of a thin or patchy lawn, or to give winter color to a dormant southern lawn, such as a bermudagrass lawn.
Overseeding a thin or patchy lawn
Older lawns may need overseeding as a result of turf thinning from drought conditions, thatch, insect damage, or disease activity. Newer lawns may be thin as a result of seeding too lightly at first planting. Regardless of the reason, if your lawn is thin or patchy, overseeding can dramatically improve the appearance of the lawn without having to perform an entire lawn renovation. Follow these steps for a successful overseeding.
- Overseeding is best done in spring or fall, when cooler temperatures and moisture prevail.
- Determine if thatch is a problem in the lawn. Dig up an area of turf. If the thatch (layer of dead roots and stems just below the green blades) is more than ½ inch thick, you should consider renting de-thatching equipment before overseeding. It is important to remove this layer so that the new seedlings will have an adequate soil layer in which to grow. De-thatching will also help your remaining turf to thrive by allowing moisture and nutrients to reach the grass roots.
- Adding a layer of topsoil (top dressing) may be necessary before overseeding, especially if the presence of tree roots has resulted in an inadequate topsoil layer. Spread a thin layer of screened topsoil over the lawn, and rake it in. Never add more than 1/4 of an inch of topsoil, or you may smother the existing lawn.
- Choose a grass seed type that is compatible with the conditions in your lawn. Once you have determined the right seed type, check the package for how much to buy for your lawn size. The package will give you recommendations for overseeding.
- Cut the lawn slightly lower than normal the day before you overseed.
- Use fertilizer at the time of seeding.
- Keep the seedlings moist! The top one-inch of soil will need to remain moist (like a squeezed out sponge) for at least the next several weeks.
- Mowing the lawn. You may mow the existing lawn, unless the ground is extremely wet or muddy. If the soil is muddy, the new seeds and seedlings may be torn from the ground. If the soil is too dry, the seeds may be picked up and blown around. Water the lawn before mowing if this is the case.
Keep in mind that a thin lawn could be the result of poor soil. Consider having your soil tested, and follow a fertilization schedule that is right for your lawn. Finally, remember to mow high and often and water when your lawn shows signs of drought-related stress.
Overseeding a Southern Lawn
Southern lawns such as Bermudagrass or St. Augustinegrass will go dormant (turn brown and stop growing) in response to cold weather. Many southern homeowners overseed their existing lawn with a northern-type grass in fall, so that the lawn will maintain a green appearance through the winter.
Steps for overseeding a southern lawn are very similar to the steps above. There are a few tips to remember however.
- The proper seed type is very important. Overseeding in the south is typically done with an annual northern grass type that will die once summer arrives. The grass type you choose should die off in heat; otherwise, it may compete with the main turf type in summer. Annual ryegrass is popular for this particular purpose. This grass type will stay green through the winter, and die off when the main southern turf type begins to emerge from dormancy in warm weather.
- De-thatch or add topsoil if necessary. See the guidelines above.
- Seed early enough in fall so that the overseeding will be growing well by the time winter arrives. Timing may vary by geographic region, so check with a local nursery professional or your Cooperative Extension Service for proper timing.
- Avoid using a fertilizer on the new overseeding. This is because southern lawns can suffer damage when fertilized during dormancy.
- Mow as needed. See the guidelines listed above.
For more information, see our lawn basic on Winter and the Lawn.