How To Overseed Your Lawn Without Aerating It

Many people aerate their lawn right before overseeding, but it isn't really necessary. In fact, it may make more sense not to aerate and overseed at the same time.

Sure, a freshly aerated lawn is dense with all those little holes for the seed to fall into, but the best time to aerate is when the grass is in heavy growth mode. That's spring for cool-season grasses and summer for warm-season varieties.

But you should overseed in the early or middle of fall when lawn weeds are entering dormancy. That way the new grass can become established before its competition.

What we're going to do here is dethatch the lawn (instead of aerating it) before overseeding. You should probably be breaking up thatch once every season anyway, especially if you are fertilizing regularly.

What You'll Need

Let's make sure you have everything you need to successfully overseed your lawn. Check out this list, then read on for some important details. 

  • Dethatching tool
  • Lawn rake
  • Seed
  • Fertilizer
  • Seed spreader (optional)

The dethatching tool is obviously critical. What kind you need depends on how big of an area you are overseeding. If you are doing your whole lawn (more than a quarter acre), you will probably be better off with a powered model.

If you've never used a powered dethatcher, they're driven by a gas or electric motor and have tines or blades that cut vertically down into thatch to break it up. This allows air and water down to the soil and root layer. It also lets grass seed get to the soil in this case.

Are you overseeding a very small lawn or just a few small patches? If so, you'll just need a dethatching rake. They are affordable and available at all home improvement stores.

Grass seed is the most obvious item on the list. Get the same variety that currently surrounds your home. You'll be much better off with fresh seed, so check the date on any seed you have laying around before using it.

Fertilizer is important. You don't need anything too strong. Get a good starter fertilizer. Anything that is advertised to be best for planting new lawns will work fine. Read the bag carefully to make sure it is a slow-release formula. Quick-release formulations may burn the new grass sprouts when they germinate.

This should go without saying, but make sure there are no germination inhibitors in your fertilizer! Unfortunately, I'm speaking from experience here. If the bag says something like "weed and feed," stay clear of it.

Pro Tip: Plan For The Right Timing

I really want you to understand why timing is so important. You're imagining a thick, gorgeous, green lawn.

I don't blame you for getting antsy!

But if you don't overseed your lawn at the right time of year, most of your work will be for naught.

Spring is a fine time to undertake a good yard project, but it's also the time when lawn weeds are germinating. There's no point in making things easier for them. Spring is the time to fight weeds, not overseed.

The heat of summer is no good either. The heat dries out the top of the soil where the seed sits. You're not going to have those aeration holes for the seed to fall into, so it will have no refuge from the hot sun. Birds love roasted grass seed, but your lawn doesn't.

That brings us to autumn. The days are getting cooler and most plant life is preparing to go dormant, if it hasn't done so already. Cool temperatures and less competition makes ideal conditions for new seed. But you're not going to go dormant. You're going into high gear to ensure a rich, green springtime lawn.

Step 1: Mow Shorter Than Usual

Now it's time to get dirty. Think of this as a weekend project. Ideally, you will have a nice dry 48 hours to do the actual work, then a few days of light, steady autumn rain. First, you need to dethatch, then overseed and fertilize within a couple days.

First thing's first. Mow a bit shorter than you normally would before you dethatch. Not only will this make the dethatching easier, but it will let more of the seed down to soil level. It would be best to use a grass catcher if you can. You don't want a lot of clippings in the way. Rake the clippings up if you have time. If not, don't worry about it.

Step 2: Dethatching

Now, let's look at the actual dethatching. This is the last step of preparation before you overseed the lawn.

Dethatching involves breaking up that layer of hard, dead roots and grass that kinda builds up between the soil's surface and the green grass above. Grass seed can't penetrate this layer, so it has to be dealt with. Aerating pokes holes in it, but we are going to shred it.

You want to break up thatch, not the roots. Different power dethatchers adjust in different ways, so familiarize yourself with the instructions. Set the machine to a height that looks good to you, then run it over a small spot. It's better to run too high the first try. You can always lower the tines and go again until you get the height right, but you don't want to churn up the roots. Use a flexible leaf rake to remove the debris.

Now inspect carefully. You want most of the thatch broken up with as little soil disturbance as possible. No adjustments are necessary with a thatch rake, but you should still follow these guidelines.

Once you got your machine set, go over your lawn, or parts thereof, only once. You aren't tilling. You're just removing thatch. You may think that this process makes your lawn looks awful, and you're probably right.

Don't worry.

Your seed will fill in the rough spots, and your lawn is going to look great next summer! Be sure to rake up as much of the thatch as possible.

💡Tip: the thatch you rake up makes a great addition to your compost bin! Ideally, let the thatch dry in the sun for a day or two and then mix it into your compost.

Step 3: Spread Grass Seed

Smaller areas can be seeded by hand. Larger areas and entire lawns are best done with a broadcast spreader or dropper. If you are using one of these devices, set it to the manufacturer's recommendation for reseeding. Don't trust that recommendation though. It's just a starting point. Try it on a small area then check.

The optimal seed density is around ten seeds per square inch of overseeded lawn. Don't drive yourself nuts here. Close is good enough.

There is no need to rake the seed down into the lawn, but you can rake it gently if you want to. If you ran into any areas that were pure thatch or dead grass and ended up with a patch of bare soil, that's where you need to rake then seed into the dirt. Be gentle and go over the area with your rake only once. Rolling or tamping the seed into the soil isn't necessary. You're going to water those seeds down into your lawn later.

Step 4: Add Fertilizer

Now that you've prepared your lawn by dethatching, raked the debris up and sown your seed, it's time to fertilize with a slow-release starter fertilizer. There are no special considerations here. Just use the right stuff and apply as usual.

Step 5: Water The Lawn

Hopefully, there is some rain in the forecast. If not, it would be best to water the overseeded areas deeply. If you have a sprinkler system, turn it on and let it run until it looks like most of the seed has been washed down into the lawn. You can use a hose sprayer as well.

For the next couple weeks, water daily to wet the top inch of soil. It's best to avoid watering at night. Wet, dark conditions are too friendly to fungus. The best time to water is within a couple hours of dawn, when possible. Don't skip daily watering just because your schedule doesn't allow you to do it at the optimal time. Keeping the top inch or so of soil moist for at least the first ten days is critical.

There you have it - that's how to overseed your lawn without aerating it. It takes some work and a little planning, but overseeding your lawn will make it thicker, healthier and greener. And you don't even need an aerator!

FAQs

Is a powered dethatcher worth it?

Powered dethatchers are useful, and they require much less effort to use than a thatch rake. But the good ones are expensive. Consider renting one. Better yet, go in on a rental with a neighbor or two.

Should I just go ahead and aerate?

You could, but aerating is best done in the spring. Overseeding is an autumn job. And aerating doesn't break thatch up as well as a dethatcher. By now, you know how important breaking the thatch is before overseeding.

When I dethatched, I was left with a lawn full of clumpy grass! What gives?

Don't be discouraged. I know. You started this project because you want a thicker, stronger lawn. But you got rid of the thatch, which is going to allow your lawn to fill out. Plus all that seed is going to be growing strong by the end of next spring. Just wait until next summer! With proper care, your lawn will choke out weeds and develop a thick, healthy turf.

Is there such thing as sowing too much seed?

Yes, there is. You don't want new grass sprouts competing with each other. The result will be weak patches. Too little seed will allow weeds to take hold. Stick to the ten seeds per square inch rule, and you'll be fine.

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Ed Kirkland
 

Hi, I'm Ed, and I've been doing lawn work since my mid teen years, picking up jobs here and there mowing and helping with basic landscaping projects. I worked at a couple different lawn care / landscaping companies throughout my college years, and now thanks to the internet I'm able to make a share my knowledge and advice with people about lawn care and landscaping.