How to Overseed a Lawn

Overseeding requires even seed spreading. But before that, you’ll need to prep your lawn. The preparation process includes dethatching, aeration, adding soil amendments, and mowing. After overseeding, you’ll need to fertilize and keep your seeds moist.

Tools and materials for overseeding your lawn

You will need the following tools and materials for your overseeding project:

• Dethatching tool
• Aerator
• Soil testing kit
• Soil amendments
• Lawn mower
• Rake
• Enriched topsoil or compost
• Lawn spreader (aka a fertilizer spreader)
• Grass seed
• Starter fertilizer

Step 1: Test your soil and amend if needed

For your overseeding project to succeed, we suggest conducting a soil test to check your soil’s condition. Your soil needs to have the proper pH level, nutrient levels, and good soil texture to support your new grass.

Your soil test will show you if your soil has any issues like too high or too low of a pH level (grass prefers a pH level of 6.0 to 7.0) and nutrient deficiencies. If you sent your soil to a soil testing lab, they will give you recommendations for soil amendments and fertilizer to add to your soil. 

Always fix soil issues before overseeding for the best results.

To learn more about soil testing, check out our articles:

• “How to Read a Soil Test Report”
• “How to Change Your Soil pH”
• “Why, When, and How to Apply Lime to Your Lawn”

Step 2: Dethatch and aerate if needed

Excess thatch (organic matter between grass and soil) and compacted soil will make it difficult for your new grass to grow. 

Too much thatch will prevent your grass from reaching the soil effectively; good seed-to-soil contact is important for germination. It can also harbor pests and disease-causing fungi. You will need to dethatch your lawn if it has a thatch layer thicker than ½-inch thick.

Meanwhile, compacted soil is harder for new grass roots and shoots to penetrate through. Soil compaction also will prevent water, nutrients, and air from getting to your young turf’s roots, stunting its growth. You will need to aerate your lawn if your soil is compacted. 

Not sure if your soil is compacted? Our guide on soil compaction goes over the signs your lawn might have this issue.

Step 3: Mow low and rake your lawn

On the day you plan to overseed your lawn, you’ll need to mow your existing grass very low. This is one of the rare occasions where scalping your lawn is acceptable and even encouraged. Mowing low makes it easier for the grass seeds to reach the soil. It also will weaken your existing grass a little bit to allow the new grass to compete.

Bag the clippings to keep the soil bare. You can compost the clippings if you’d like.

Then, rake your lawn to remove debris that will prevent good seed-to-soil contact.

Step 4: Add a thin layer of topsoil

To add some nutrients to the soil, you can spread a thin layer of enriched topsoil over your entire lawn. Enriched topsoil is loamy soil mixed with organic matter that will help nourish your new grass. You can also use compost instead.

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

Step 5: Spread seeds evenly

Add 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, “How to Grow Grass”.

Now, it’s time to overseed. 

Overseeding a large area

If you’re overseeding a large area or your whole lawn, we recommend using a broadcast spreader or a drop spreader. You can also use a slice seeder if your lawn is very damaged.

To ensure even coverage, practice bi-directional seeding by spreading half of the seeds going from north to south. Then, make another pass with the other half from east to west.

Overseeding a small area

You can use a handheld spreader to overseed small patches. Spread the seed as evenly as you can.

Step 6: Ensure good seed-to-soil contact

Once you’re done spreading the seeds, you’ll need to tamp them down into the soil to ensure good seed-to-soil 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.

Step 7: Apply starter fertilizer

Your new grass will need nitrogen, phosphorus, and potassium (collectively called N-P-K) to grow strong. Starter fertilizer is specially formulated to have more phosphorus and less potassium to support root growth. 

You can apply starter fertilizer after overseeding, but you can also wait until after it has germinated – about six to eight weeks after overseeding. It may even be safer not to fertilize and seed simultaneously, but any problems that arise from doing these at the same time are usually because the wrong fertilizer is used. 

If you want to know more about fertilizing your grass, see our articles:

• “A Complete Guide to Fertilizing New Grass”
• “Will Fertilizer Kill New Grass?”

Step 8: Water your lawn

Lastly, you’ll need to water your new grass seed to make it sprout. Water lightly so you won’t disturb the seeds. You will need to keep your new grass moist; drying out means dying out. Generally, this means light watering every day – possibly multiple times a day.

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

• “How Often to Water Grass Seed”
• “How Long to Water New Grass Seed”

FAQs about overseeding

What time of year is the best time to overseed?

The best time to overseed is late summer to early fall if you have cool-season grass and late spring to early summer if you have warm-season grass.

Can I apply weed control while overseeding?

Generally, you can’t apply weed control while overseeding. Pre-emergent herbicides will mess with the grass seed germination, while most post-emergent herbicides can’t be applied to new grass. The University of Georgia Extension recommends waiting until after you’ve mowed your new grass three to four times.

Right now, the only weed control product that’s safe to apply at the same time as overseeding is mesotrione (such as Tenacity). It acts as a pre- and post-emergent selective herbicide.

How do I care for new grass?

Here is a short guide on caring for new grass:

• Water frequently. Keep your lawn moist as your new grass needs time to develop a strong root system.
• Mow only after the grass is 3 to 4 inches tall. Mowing too early will stress out your grass.
• Avoid weed control products. We talked about this above, but weed control products can injure your new grass. Stick to hand-weeding.
• Avoid foot traffic. As much as possible, don’t walk on your new grass until after at least a month.

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’s pros can overseed your lawn, fertilize it, and mow it when it’s tall enough. They can also aerate your lawn in preparation for overseeding. Hire a pro through Lawn Love today.

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