If your lawn is brown, patchy, or thinning, why not overseed? Overseeding is broadcasting new seed over your lawn to fill in gaps where grass has died. Overseeding your lawn fills bare spots, chokes out weeds, and creates a healthier, fuller lawn.
When to overseed
It is important to know which seed type (cool season or warm season) grows in your state. In northern states (see map below), cool-season grasses withstand freezing winter temps and blankets of snow but go dormant (brown) in the warm summer months. Across the southern U.S., warm-season grasses thrive in the sweltering summer months and take a well-earned rest (dormancy) during the mild winters.
Late summer or early fall works well for cool-season grasses. Late spring or early summer works best for warm-season grasses. You want to put the seed down right before the existing grass starts its growth curve.
What seed should you use?
Consider which variety will work best in your yard’s sun/shade conditions. For example, a cool-season variety such as Kentucky bluegrass loves full sun, but perennial ryegrass and fescue will grow in partial shade. Remember that most shade-tolerant varieties require some sun each day.
Note: If you are buying cool-season grass, you may see seed mixes that consist of bluegrass, fescue, and ryegrass, for example. This helps to accommodate different growing conditions across the yard. Warm-season grasses are usually sold as single varieties.
Cool season grasses
- Shade tolerant: perennial ryegrass, creeping red fescue, other fescue varieties
- Sun: Kentucky bluegrass
Warm season grasses
- Shade tolerant: St. Augustine, centipede, bahia
- Sun: bermudagrass
- Shade tolerant: tall fescue
- Sun: Zoysia
Pro Tip: If you want your warm-season lawn to have winter color, you can overseed in early fall with cool-season grass. This combination will make your grass green and lush year-round.
Consider the seed variety in addition to the grass type. For example, even though you can overseed cool-season grass in early spring, some grasses such as tall fescue may not do well if overseeded at this time of year. Consider searching on your state’s Cooperative Extension Service website for more information.
How to overseed a lawn
Before you start: Run a soil test with a DIY kit or send a sample to your state’s Cooperative Extension Service. Allow a week or two for processing.
1. Cut the grass
Mow the lawn at 1 ½ inches to 2 inches. Use the bag attachment to collect the clippings.
2. Prepare the soil
Both dethatching and aerating help water, nutrients, air, and sunlight reach the roots.
- Dethatch: Dethatching takes off the dead layers of decomposed grass and debris from the soil. You can use a thatch rake, dethatching machine, or power rake. Go over the lawn with the mower and bag attachment to collect the thatch.
- Aerate: Core aeration pulls plugs or cores from the soil, opening up the lawn for Step 3. As long as you are working in dry weather, there is no need to rake up the soil plugs.
- Apply compost: Put down ½ inch to 1 inch of compost. Rake it in with a leaf rake.
- Fertilize: If your soil test indicates that you need a starter fertilizer, apply it now using a seed spreader. Note: Some experts say this is unnecessary and that the extra phosphorus can be harmful to local water systems. Contact your local Cooperative Extension agent for advice.
3. Plant seed
After preparing the soil, it’s time to put down the new seed. Look at your seed instructions for the rate of application. Use a hand spreader or a push spreader for the best results. Use the back of a rake to mix the seed into the compost layer.
Pro Tip: Spread the seed vertically and then go back over the lawn horizontally with the spreader to ensure you get good coverage.
Water your lawn once or twice per day to ensure the seed stays moist. Don’t water so much that the seed is washed away. Keep up these light waterings until the new grass is as tall as your existing lawn. Once the lawn is established, switch to watering twice each week. Deeper, less frequent waterings encourage the grass roots to grow deeply into the lawn.
Key Takeaway: If you fail to water, your lawn will fail. Consider an automatic watering system to ensure the grass is moist during this critical period.
Make sure your new grass grows
To ensure your grass grows, keep foot traffic on your lawn to a minimum for the next three to four weeks. Don’t be an eager beaver when it comes to mowing your new, lush lawn. Wait three to four weeks after seeding to mow the lawn, and use your lawn mower’s highest setting. Some say you can start to mow again as soon as the new grass reaches 1 to 2 inches, while others prefer to wait until it is a bit higher.
FAQ about overseeding
Weed and feed products contain a pre- or post-emergent herbicide and fertilizer. According to the experts, most of the herbicides in these products prevent germination, so they are not recommended when overseeding.
However, certain pre-emergent herbicides are developed to be used with grass seed and will be marketed as such. Check the label. You may want to use one of these pre-emergents for crabgrass control if you are planting cool-season grass in early spring. It is not necessary if you’re planting cool-season grass in the fall.
Yes. If you have a few patches that need overseeding, you can follow the same steps outlined above.
It depends on your lawn. Homeowners may need to overseed as often as once per year or as little as every few years. Consider it a part of your recurring lawn care to help ensure an optimal, healthy lawn.
Fun Fact: Cornell University recommends that sports turf managers overseed football fields weekly for optimum density.
Simple steps guarantee a great lawn
Follow these four, simple steps to correct patchiness and improve your lawn health throughout the yard. Remember to choose the best variety for your climate and the sun/shade conditions of your lawn. With a little care and attention, your lawn can remain dense and lush year-round.
Want to know more about overseeding? Check out our article, “What is Overseeding?”
Don’t have time to overseed your lawn or know where to start? You can always call on a local lawn care professional to help you get the job done right.
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