7 Steps to Sowing Grass Seed on Existing Lawn (Don’t Just Throw It)

By   | Last Updated :   October 14, 2022 | Filed In :   DIY & How To

Tired of the bare and grassless patches on your lawn? Time to turn them from lacklustre to lush with overseeding.

Overseeding your lawn takes a bit of time and effort. You can do it in seven steps, starting with picking the right grass seeds. Then mow, dethatch, aerate and fertilise your lawn. Once done, you can simply spread the seeds by hand or with a seed dispenser. Finally, water your lawn and watch your efforts materialise into a lush lawn.

That’s right. You can sow grass seeds on an existing lawn, but it’s more than just throwing seeds here and there.

overseeding before after

Image credit: @drewslawnandlandscape

When to add grass seed to a lawn

The best time to reseed your lawn is in spring and autumn. That’s when the conditions are mild yet wet, something that grass seedlings enjoy very much.

You can overseed your lawn in summer too but check the weather forecast beforehand. Long, dry spells are bad for seeds and they may die before germinating.

How to sow grass seed on an existing lawn

The best way to overseed an existing lawn starts with picking the right seeds. Next, mow, dethatch, aerate, feed and overseed it. Finish by watering your lawn and voila!

overseed patchy lawn

Reapair a patchy lawn by overseeding. Image credit: @oregreen_gardening

Step 1 – Pick the right seeds

The first and most important step is to pick the right seeds for your lawn. Don’t just grab the first seed pack you find. Otherwise, you might end up making your lawn look rather wild and unkempt with different kinds of grass.

Start by matching grass seed to the existing lawn. To do so, figure out the type of grass you already have in your lawn. Look at the blades of the grass and decide whether they’re flat or fine.

Also, consider the environmental factor. This includes the soil, temperature, sunlight, water and drainage needs. A seed mix of perennial ryegrass is ideal for a wear-tolerant lawn, whereas a pure fescue seed blend is suited for a shady, dry or ornamental lawn. 

Tip: If you’re not sure about the best grass seed for overseeding, look for a seed mix containing both ryegrass and fescue.

Step 2 – Mow the lawn

A lot of people wonder, “is it better to mow existing grass before or after overseeding?”, we recommend mowing the grass before overseeding. This will give the seeds a better chance to reach the soil and germinate.

So, give your lawn grass a good trim. You can cut it slightly shorter than you normally would: 25 to 30 mm is ideal. But make sure to not scalp your lawn. You’re only trying to open up the turf for overseeding. Once the job is done, bag or rake up the clippings.

Mowing your lawn before overseeding has several benefits. It keeps you from overwhelming your lawn with too many seeds. It also reduces competition from surviving lawn grasses and allows for sunlight to reach the seeds.

Step 3 – Remove debris, weeds and thatch

While preparing the lawn for seeding, clear any debris from it. This will keep the grass seeds from getting trapped. Also, manage any broadleaf weeds at this stage. Manually rake them out or use an organic weed killer.

Now, dethatch your lawn. Thatch is mostly a layer of dead and dry grass on top of the soil. Break it up with a thatch or leaf rake. You can also use a powered scarifier for a large lawn.

Dethatching will allow water and nutrients to easily reach the new seeds. This will improve the germination rate so your patchy lawn becomes green and lush again.

Step 4 – Aerate the lawn

You will also have to loosen the lawn soil by aerating it. Poke holes in the soil with a garden fork, you can also use hollow tine or core aerators to get the job done easily.

Aerating your lawn will help water, air and nutrients to reach the soil. It will also loosen compacted soil and create a space for new grass seeds to germinate successfully.

Tip: Make sure the soil is slightly moist before you start aerating. Overly dry soil is hard to penetrate and you may end up accidentally damaging your turf while working on it.

aerate lawn before overseeding

It’s important to aerate the lawn before overseeding. Image credit: @shadowgreenlawncare

Step 5 – Apply lawn feed

Grass seedlings are weak and vulnerable. They may even face lawn pests and birds pecking them before they grow, but don’t be disheartened. To ensure that the seedlings survive and thrive, apply a lawn starter feed. It’s high in phosphorus and will encourage your grass seeds to take root quickly.

You can also opt for quick-release starter fertiliser. Apply it in areas where you will plant the new grass seeds. It will offer a strong hit of nutrients that will help the seedlings establish themselves.

Tip: Don’t use a fertiliser designed for mature grass. These formulas contain little to no phosphorus and don’t promote seedling growth.

Step 6 – Sow the seeds

You can’t just throw grass seed down on an existing lawn. You need to properly sow the seeds, otherwise they may end up just sitting on top of the soil and may never germinate. 

For smaller patches, you can just sprinkle grass seed on lawn by hand. But if you have to overseed larger areas, consider using a seed dispenser. 

Wondering how to re-sow a lawn? Well, make sure to sow the seeds evenly. It’s pretty easy, but pick a day when the air is calm. Overseeding your lawn on a windy day will blow the seeds around and put your efforts to waste.

Once done, you can loosely rake in the seeds. Also, cover them lightly with fine mulch or topdressing material. This will help to maintain moisture and warmth and will also protect the seed from birds.

Tip: Don’t mix grass seed with topsoil when overseeding. Topsoil lacks nutrients for healthy germination and may suffocate the seedlings.

seed dispenser overseeding

Use a seed dispenser for best results.  Image credit: @anchorlandscape

Step 7 – Water the lawn

The final step is to water your freshly sown lawn. Grass seeds need moisture to properly germinate. Dry conditions can kill the seeds so continue to water the lawn for several weeks after sowing.

Use a fine spray to water your lawn. Use it with care as you don’t want to wash away your seeds or make them clump together in certain spots.

Tip: Once the new grass grows, you can water the lawn for longer periods but do so less frequently.

Caring for lawn seedlings

Sowing grass seeds on an existing lawn will help you grow a healthy, lush lawn. But to maintain it, you will have to care for the seedlings.

Make sure to water the lawn frequently, even after the seeds sprout. You can cut grass 2 to 4 weeks after overseeding: simply mow as you normally would.

At the same time, avoid using heavy machinery until the seedlings are 3 inches tall. You can also begin fertilising the lawn 5 to 6 weeks after overseeding. By this time, your new seeds will be sprouted and rooted.


Can I just throw grass seed down on an existing lawn?

It’s not a good idea. The seeds may stay on top of the soil without ever germinating. (If the wind doesn’t scatter them about, that is, or if birds don’t peck them out). It’s better to work them into the soil. This means adding over them some topsoil if necessary.

Can you throw grass seed on an existing lawn in any season?

You can reseed an existing lawn in spring or autumn. You can also do it in summer if the soil isn’t too compact. Work the seed into the soil or mix it with a fine layer of topsoil to ensure it germinates. 

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