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Overseeding A Lawn

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What to Consider When Overseeding a Lawn
Someone using a measuring wheel to measure a lawn for overseeing.

Overseeding a lawn means planting grass seed directly into your existing grass. You don't have to break up your lawn or soil. It can help prevent weeds from taking over your lawn. 

When to overseed depends on where you live. Overseeding a lawn in fall is ideal if you’re growing cool season grasses. That's because the soil is still warm enough for seeds to germinate and the cool air helps grass to grow a strong root system. Kentucky bluegrass, perennial ryegrass and fescue are cool season grasses. Cool fall weather starts earlier in the North, so overseed your cool season grass by late summer or early fall if you live in there. 

Late spring or early summer is ideal for overseeding warm season grasses in the South. Bermuda, centipede, Saint Augustine and zoysia are warn season grasses. If you’re overseeding a lawn in spring or early summer, give your seedlings frequent, light waterings. That helps them get established before hot, dry weather sets in.

There are a few things to do before you start overseeding a lawn: 

  • Figure out the size of your lawn. A measuring wheel can help. Multiply the width and length of your lawn to get the square footage. If you have more than one grassy area, find the square footage for each section and add the totals together. 
  • Stop fertilizing for at least a month before overseeding. The fertilizer makes your grass grow faster, which makes it harder for the new seeds to take hold.
  • Identify your grass type or the type of grass you want to grow, so you can manage it appropriately. To do this, consider the climate of your growing region, look at the shape of your existing grass blades and feel the texture of the existing grass. Use our guide on Types of Grass Seeds to help identify what's already growing. Learn more about different kinds of grass with our Lawn Care page. 
  • When determining how much grass seed you need, don't guesstimate, calculate. Know exactly how much you need with our project calculators.

Mow and Dethatch Your Lawn

Mow your lawn so that the grass sits above the soil line. Ideally, it should be an inch to an inch and a half. This will let the grass seed get enough sunlight and make good contact with the soil. 

Next, use a thatch rake or power rake to remove any thatch you find. This is called dethatching. Thatch is a spongy layer made up of dead grass blades, stems and roots mixing with living plant parts. A thick layer of thatch can lead to disease and insect problems if you don't remove it. It  can also keep grass seeds from germinating. 

To dethatch, rake your lawn in one direction and give it another pass in the opposite direction. The tines on the rake will pull up the thatch along the way. Be sure to take the thatch off the lawn when you’re done.

Aerate Your Lawn

Another way to remove thatch is to aerate your lawn. This combs your grass and kicks out debris. It also loosens the soil so air and water can reach the roots. Your grass seed will also grow faster and better. It's especially important to aerate lawns that are compacted by heavy foot traffic. 

A core aerator is a great tool for this job. To use the core aerator, move it across the lawn in straight lines until you've gone over the entire yard. Do a second pass perpendicular to the first one if needed. The core aerator should pull up plugs of soil instead of just punching holes in the ground. This helps break up the compaction. Leave the plugs on the ground and they'll disintegrate in a couple of weeks.

Improve Weak Spots

If your lawn has bare spots, cover them with topsoil. This will improve the quality of the soil and help the grass grow. For areas with water drainage problems where grass doesn’t grow, add a thin layer of sand and smooth it out with a rake. Sand helps the grass germinate faster and develop a good root system.

How to Overseed and Fertilize Your Lawn

Now you can spread your grass seeds evenly around the lawn using a broadcast spreader, drop spreader or handheld spreader.Then, apply the lawn fertilizer that works best for your type of grass. Slow-release fertilizer provides nutrients gradually, for as long as three months in some cases. 

Lightly water the lawn immediately after overseeding. Continue to water it frequently, about three to four times daily for the first several weeks, to help the seeds germinate. Once the grass is an inch tall, cut back to watering once a day.

For more information, read our guide on How to Fertilize Your Lawn.How to Feed Your Lawn.

Overseeding Maintenance

Once you know how to overseed a lawn, it’s easy to maintain it. Keep mowing the grass to two inches tall for the rest of the season. Always wait until the grass is dry before you mow.  

Fertilize the lawn about six weeks after you sow the seed. Apply a pound of quick-release nitrogen fertilizer for every thousand square feet of lawn space. For example, if your lawn is 5,000 square feet, you would need five pounds of quick-release nitrogen fertilizer for your specific grass type. Repeat the feeding in another six weeks or as directed on your product label.

Overseed your lawn to keep it healthy, repair damage or fill in bare spots. Remember to identify your grass type before you begin. Then mow, dethatch and aerate your lawn to help the grass seed make contact with the soil and let air, water and fertilizer reach the roots. After sowing the seeds, lightly water them and keep watering a few times each day for the first several weeks. Then water once a day. 

Wait six weeks before fertilizing. Apply more fertilizer as directed on the product label.

Need a product, tool or material? Use our mobile app to search by voice or image. If you need some extra help overseeding your lawn, consider renting an overseeder, power rake or aerator with our overseeder rental to get your project done. Use once, then bring it back - no maintenance required.