Best Time to Aerate and Overseed Lawn: Complete Guide

Weather conditions, wear and tear, pests and diseases can take a toll on your once green carpet of grass. As a result, your lawn starts to have bare spots, burned patches, thinning grass and generally weakens. Luckily, overseeding is an option to bring your grass back to life.

Compared to starting a new lawn from scratch, planting a new lawn over an old one is easy; it does not take so much time and resources. The overseeding process simply involves dethatching, raking, aeration, sowing and maintenance.

What is overseeding?

Overseeding is simply adding new grass seed to your existing lawn without turning or perforating the soil. This will greatly improve density and add more color to your lawn.  Overseeding usually involves the entire lawn or sometimes targeting specific patches or bare spots.

This process is sometimes done after lawn aeration to allow air, water and essential nutrients to penetrate turf and encourage optimal root growth. However, with fear of seeds getting trapped in perforated holes, overseeding can successfully be done without aeration.

Why overseed your lawn?

There are plenty of benefits that comes with overseeding a lawn. They include the following

  • It improves aesthetic value of a lawn by repairing burned or bare spots to make grass look luscious and healthy.
  • Increases grass thickness and tolerance to weathering, wear and tear, weeds and any other environmental stressors.
  • It also feel fabulous walking or relaxing on a carpet of thick grass. Lawn overseeding therefore makes your outdoor living luxurious and special.
  • Overseeding reduces lawn maintenance costs by making grass strong and tolerant to pests, diseases and weeds. There is no much worry about weeds or pests control expenses and associated risks to the environment.
  • Helps in keeping the environment clean and safe. Chemical fertilizers and pesticides will not be necessary. After overseeding and watering grass becomes naturally healthy, strong and thick.
  • Reduces soil erosion by making grass to have a well interconnected network of root system that bind soil together. This greatly reduces surface run-off and soil loss during a downpour or speeding winds.
  • Overseeding is the best way to create a uniform-looking lawn without having to do an individual spot renovation. This saves time and produces better lasting results.

Best Time to Aerate and Overseed your lawn

The time to overseed a lawn depends on your geographical location which also determines the type of grass to plant.

The best time for overseeding cool-season grasses in northern regions with cooler climates is late summer to early fall to give seeds about a month to develop before the region’s first frost. If you miss it in fall then Spring is the second best time to overseed but should be early enough before summer heat begins.

The warm soil supports seed germination while cool fall air stimulates grass growth. During this periods, soil moisture is steadily constant and favorable for germination. Tough, warm-season lawn weeds, such as crabgrass are less active in fall too thus no serious threat to the germinating grass.

In the south, southeast, and southwest, where average temperatures are high and summers are long, overseed in mid spring or early summer. This is the time warm-season grasses enter active growth and soil is warm enough for seed to germinate. In fall and winter warm season grasses become dormant.

How to Overseed Lawn – Steps

To make the job faster and for even distribution of seeds, use a seed spreader. For large lawns consider using broadcast spreaders and handheld spreaders for smaller areas.

1. Dethatch your lawn

When weeds and moss take over your lawn, it is left with some patches that have less amount of grass than the rest of the lawn, and some do not have any grass at all. At times, the grass in these patches may have turned brown or discolored.

Before you begin your overseeding work, you must first get rid of the unwanted grass and debris in the patches. Lawn dethatching is important because the overlying thatch and organic material that comprises of dead green matter can prevent the new grass from germinating or doing well.

You should, therefore, get rid of such matter to allow sunlight, nutrients, and water to penetrate the soil. You can get rid of the thatch by use of a mechanical dethatcher, which you can easily get from a local agricultural outlet near you.

2. Mowing the existing grass

Before planting your new lawn, you need to get rid of the browned or unhealthy grass from the patches in your lawn. Also, the size of the grass needs to be reduced to a level of not more than 1 ½ inch. This allows sunlight and nutrients to reach the roots of the new grass.

But even as you do your mowing, remember to remove the cuttings to create room for better seeding when the time comes. You can use your handheld mechanical mower to do the job. When mowing, ensure to overlap your paths slightly to achieve a uniform grass height all over the lawn.

3. Aeration the lawn

The next step in land preparation when overseeding is aeration. Aeration of the lawn is important because, by this time, the soil on the lawn is usually very compact such that the roots of the new grass may not go deep into the ground enough for enhanced growth.

We advise on using the hollow tine aerator over the solid tine one. This is because the solid tine aerator only pushes the soil further down, hence compacting it even more.

This will not augur well for the new grass because its roots will not penetrate deep into the soil. On the other hand, the hollow tine aerator breaks the core of the soil, allowing the roots of the new grass to penetrate deep.

4. Sow the new grass seed

Then comes the main event of the process; the sowing of the new grass seed. But before this, you should have your soil tested so as to decide what type of grass does well in your soil and if there is any soil amendment to be done.

You can take some little samples of your lawn soil to the agricultural department near you for testing. When it comes to sowing the new grass seed, I advise on the seed spreader so that you can achieve a uniform distribution of the seed. Ensure to overlap each pass, to eliminate bare spots in the lawn.

5. Thorough watering

Immediately after spreading the seeds, water your lawn and continue on a daily basis until the seeds germinate. Water is a very important aspect of overseeding and when done correctly seeds will germinate within a period of two weeks.

When watering, get soil soaked but do not flood the lawn. Once seeds are germinated, water every few days or as directed for that type of grass. When the grass is getting established avoid activities on the lawn including mowing until the new grass attains the same height as the existing lawn.

6. Provide care and maintenance

Sowing the seed is not enough; it must be followed by effective maintenance of the seed until it grows to the level of the old grass. After you have sown the new grass seed, you can apply little amounts of starter fertilizer and ensure to cover it with a thin layer of topsoil.

The thin layer of soil also help hiding the new seed from the birds’ eyes and elements. It also gives the seed a solid medium for proper and faster germination. Besides, the seed will be deeply rooted in the soil and will not be displaced when watering the lawn.

Alternatively, you can mulch the new grass seed which also reduce the loss of water through evaporation. This way, you can be assured of almost 100% germination of the new grass seed. When the grass is grown, do not mow it until it is ¾ inch taller.

Do I need to remove old grass before seeding?

Whether or not you need to remove old grass before reseeding depends on the condition of the existing grass in the patchy areas. If it is browned or heavily infested with weeds and moss, then you can consider killing it altogether. If it does not have so much weed or is still in good condition, then you can opt to kill only the ones you want to do away with.

To kill all the grass on the patchy areas, you can spray it with a chemical kill. And as you do that ensure to bring the nozzle of the sprayer close to the grass to avoid killing even the one you would want to retain.

The only disadvantage in using a chemical herbicide for grass killing is that once it gets into the soil, it may affect the normal proper growth of the existing and the new grass because of the surge in pH levels. You may have to wait for some time before you reseed

Alternatively, cover the old unwanted grass with a black ploy film. This prevents sunlight from reaching the grass, hence killing it, but this is viable if you want to remove the old grass altogether. We found the best method of removing old grass from the patchy areas is by using a sod cutter.

How long after killing grass can I reseed?

Whichever method for killing the old grass you decide to go with, the grass takes between 2 and 3 weeks to die, after which you can sow the new seed. Dead grass is usually dry and brown, resembling hay.

And because it dies together with moss and weeds, you will need a rigid tine rake to remove it. If you are not a handy person, be prepared to use some bits of muscle in this process.

Do not throw the dead grass away yet; you might need it for mulching after sowing the new grass seed. You could also use the grass for composite and use the fertilizer to grow veggies in your kitchen garden.


While you can decide to overseed a lawn on your own, hiring a professional will give you the best results ever. The expert will come with special equipment, carry our thorough analysis and establish what is best for your lawn.

Bare spots and thin patches in your lawn may have been caused by other issues and an expert will be the right person to rule out if overseeding is really what will solve the problem.


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