How to Overseed a Lawn

Overseeding involves spreading new grass seed over your thin, tired lawn to give it a boost. If done right, it can turn your grass so green that it will be the envy of your neighbors. 

Before spreading any seed, do some prep work like dethatching, aerating, mowing, and adding soil amendments. Then, spread seeds evenly, fertilize, and irrigate frequently to keep the seeds moist.

In this article, we’ll walk through everything you need to know when overseeding a lawn to get the most out of your project.

Skill level: Intermediate Estimated time to complete: 8 to 9 hours for a 10,871-square-foot lawn Project cost: $150 to $200

Supplies needed

Here are all the tools and materials you need to keep handy for your overseeding project:

• Dethatching tool
• Aerator
• Screwdriver 
• Lawn mower
• Fertilizer spreader
• Rake
• Enriched topsoil 
• Grass seed
• Starter fertilizer

Choose the right grass seed 

The best seed depends on your existing grass and what you want to improve. If you have Kentucky bluegrass, overseed it with tall fescue to boost its disease resistance. Conversely, if you have fine or tall fescues, adding Kentucky bluegrass can give your lawn a lusher, greener look. 

Take a moment to look at what your lawn is doing well and where it’s struggling. Think about what you want from your grass so you can choose the right seed. You can also visit your local garden center for help. 

Dethatch and aerate the lawn if necessary 

Thatch is a layer of undigested roots, stems, leaves, and other organic material that accumulates between the grass and soil. It’s beneficial for your lawn as long as it’s less than half an inch thick. But if it’s more than that, it can block seed-to-soil contact and prevent water and nutrients from reaching the roots. 

You can use a manual dethatcher, but if you have a large lawn, I recommend using a powered one. Here’s how to use a dethatching rake:

• Move the rake in a back-and-forth motion across the lawn. 
• Apply firm pressure for proper thatch penetration. 
• Use long, steady strokes to lift the thatch.

Check out our guide on how to dethatch your lawn and what thatch is for more information. 

If your soil is compacted, aerate it so the new grass roots can grow deep and get the water, nutrients, and air they need. 

Not sure if you have compacted soil? Try the screwdriver test. Push a screwdriver a couple of inches into the soil. If there’s resistance, you have compacted soil. 

For more information, check out our articles on what lawn aeration is and how to aerate your lawn. 

You can skip aerating your lawn if the soil isn’t compacted. In that case, check out our article on how to overseed without aerating for more information. 

Mow low

Dr. Grady Miller, Professor and Extension Turfgrass Specialist at North Carolina State University, says, “Mow your existing grass to an inch or shorter before overseeding, as shorter grass gives the seeds better access to the soil. You also won’t need to mow too soon afterward and disturb the new seedlings as they begin to grow.” 

Bag the clippings as you mow so they don’t get in the way of the seeds.  

Rake up debris

After mowing, rake your lawn to remove any loose grass clippings, fallen leaves, or debris that prevents good seed-to-soil contact. Rake a bit deeper to loosen the top layer of soil and create a better surface for the seeds to settle. 

Add enriched topsoil 

Add a thin layer of enriched topsoil over your entire lawn. Enriched topsoil is loamy soil mixed with organic matter to nourish your new grass. 

Use a fertilizer spreader to add a ¼-inch layer of topsoil over your existing grass. To learn more, you can read our guide on topdressing your lawn.

Spread seeds evenly

Pour the grass seed into your lawn spreader according to the label instructions for overseeding. If you need to make two passes, load half of the seeds you need and then add the other half after going over your lawn for the first time.

How much grass seed do I need? It depends on the type of grass you want to plant and the size of the area you’re overseeding. Generally, the back of the bag should tell you how much grass seed you need per 1,000 square feet. To learn more, check out this formula in our guide on how to grow grass.

If you’re overseeding a large area or your entire lawn, I recommend using push spreaders. There are two types: 

• Drop spreader: Drops seed directly underneath as you push it, giving you more control over the target area. Ideal for smaller lawns that are less than 5,000 square feet. 
• Broadcast spreader: Distributes seed in a broad, overlapping pattern that helps you cover large areas quickly. Best for lawns larger than 5,000 square feet. 

You can use a handheld spreader to overseed small patches. It spreads seed in an arc like a broadcast spreader, but at a smaller scale. Check out our article on types of fertilizer spreaders for more information. 

Once you’re done with overseeding, tamp the seeds down into the soil for good soil-to-seed contact. There are a few ways you can do this:

• Use the back of your rake to press down on the soil. 
• Rake the seeds into the soil.
• Run a lawn roller lightly over your lawn.

Apply starter fertilizer

Apply starter fertilizer to give your new grass the nitrogen, phosphorus, and potassium it needs to grow strong. Starter fertilizer is specially formulated to have more phosphorus and less potassium to support root growth. 

I caution against using weed and feed fertilizers, as the herbicides they contain can prevent new grass from growing.

Check out our guide to fertilizing new grass for more information. 

Water well

Water your lawn lightly to keep the soil moist as the new grass sprouts. You need to water once or even twice a day, depending on the weather, to keep the soil from drying out. Keep watering daily until the new grass is as tall as the established grass. If you notice any signs of overwatering, like puddles or spongy soil, cut back on watering immediately. 

“Water is essential for seed germination, and once it starts, it can’t be undone. Some people wait for rain if it’s expected within a week, while others start watering right after seeding to keep the surface moist. There isn’t just one right way, but keeping the soil consistently moist is key,” says Dr. Miller.  

The best time to water your lawn is between 5 a.m. and 9 p.m., when there’s less wind and evaporation. If you need to water a second time, do it in the early evening, around 6 p.m. 

If you want to know more about watering your grass seed, check out our articles: 

• How Often to Water Grass Seed
• How Long to Water New Grass Seed
• When Is the Best Time to Water Your Grass?

That’s all the steps involved in overseeding your lawn. Avoid mowing the newly seeded grass until it’s at least four inches tall. At that point, you can return to your regular lawn care routine. I also recommend avoiding foot traffic on the new grass to prevent stressing it out. 

FAQs

Hire a pro to overseed your lawn

The process of overseeding can be a bit time-intensive, especially when it comes to preparing your lawn. If you don’t have the time or energy to do all of this, try calling a pro for an extra set of hands. 

Lawn Love pros can overseed your lawn, fertilize it, and mow it when it’s tall enough. They can also aerate your lawn to prepare it for overseeding. Hire a pro through Lawn Love today to get the job done right at a price you love. 

Main Image Credit: GarkushaArt | Adobe Stock