Exactly How To Overseed A Lawn

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Is your lawn looking a little lousy? It might be time to overseed. In this guide we take you through exactly how to overseed your lawn.
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A worn-out lawn happens to the best of us. Even the most well cared for turf will age unless you overseed.

Overseeding is the secret to a long-lasting, evergreen lawn.

In this guide, we take you through how to overseed a lawn and bring the sparkle back into your yard.

Table of Contents

What is overseeding?

Overseeding is the process of sowing new grass seeds over your existing lawn without digging up the soil. It’s a quick and simple way to revitalise a tired-looking turf and keep the grass looking thick, healthy and weed-free. You can also use it as a chance to introduce improved grass varieties to your lawn.

As grass gets older, the rate at which it produces new blades slows down. If left unchecked, this eventually leads to a thin, discoloured lawn that’s easily overrun with weeds. Overseeding generates fresh, younger grass that quickly fills out any patches, improves the colour of the lawn and helps to ward off weeds and disease.

old patchy lawn thats turning brown compared to an thick full lawn
Old unkept lawn vs an overseeded lawn

When most people start overseeding, their lawn is already damaged so it takes a while to return to its prime. Seasoned lawn experts overseed every year as part of their regular lawn care, using it as a preventative measure to stop their lawn deteriorating.

Overseeding is also used to provide colour to warm-season grasses in the winter. Warm-season grasses don’t deal well with colder temperatures. By overseeding them with a cold-season alternative before the winter, you can ensure year-round colour and growth.

How to prepare a lawn for overseeding

For the grass seed to sprout, it needs to make contact with the soil. Preparing your lawn for overseeding is all about maximising soil contact, and therefore maximising the chance of success.

Remember: failing to prepare is preparing to fail!

Here are three things to do before you overseed your lawn:

Step 1: Understand the problem

Before you spend your time and money overseeding your lawn, you need to understand what problems led to your existing lawn’s demise.

Once you’ve determined the cause, make sure to fix this before overseeding the lawn. Otherwise, your new turf will suffer the same fate. Most problems are easy enough to solve, and you can incorporate the fix into the overseeding process.

Some common issues include:

  • Compact soil
  • Using the wrong grass variety
  • Using an outdated grass variety
  • Poor soil conditions
  • Poor water drainage
  • Excess thatch
  • Lack of proper maintenance

 

An easy way to diagnose problems with soil condition is to do a soil test to determine the type and pH of your soil. The results of the test will tell you if you need to make any amendments with a starter fertilizer. The other issues should be easy enough to spot by sight.

Step 2: Mow the grass

Set your mower to its lowest setting and mow the lawn.

man cutting the lawn
Always mow the grass before overseeding the lawn

Cutting the existing grass as short as possible will expose the soil surface, and also make sure the new grass seedlings get enough sunlight and water.

Bag your clippings if you can. If you can’t, then you can take care of them in the next step.

Step 3: Rake and aerate

Raking your lawn helps to remove any debris (including grass clippings) and also loosens the top layer of soil.

If you identified a problem with excess thatch, this is the time to dethatch your lawn. Thatch is a layer of organic matter that sits between your grass and the soil. If the layer is too thick, then it can prevent seed germination. You might be surprised how much debris gets uprooted after dethatching!

woman raking up grass debris from lawn
Woman rakes up the debris after dethatching

Core aeration isn’t always a necessary step, but a great time to do it is just before you overseed your lawn. Aeration helps to ‘fluff up’ compacted soil, allowing air and moisture to flow. An aerated lawn will be better able to absorb nutrients and pass them onto your grass seeds.

If your lawn needs a lime application, after aeration is the best time to do this. Lime is most efficient when it can penetrate deep into the soil. Check out our guide on how to tell if your lawn needs lime if you’re not sure.

You could also topdress your lawn to fix any unevenness that may have appeared as a result of the bare patches.

How to overseed a lawn

Once you’ve done all the prep and chosen the seed, you’re ready to get going!

Here are 4 easy steps to follow to overseed your lawn.

Step 1: Dress the lawn with a thin layer of compost

We prefer to topdress grass seed with compost rather than topsoil because compost is a natural fertilizer and will provide essential nutrients to your new and existing grass. You don’t need a lot, a coating around 1/4 of an inch thick is enough.

If you want to add lime to your lawn, or want to use a different type of fertilizer, do this before layering the compost. Be careful not to over-fertilize!

Fertilizers that contain phosphorus stimulate root growth and aid early development of your lawn. However, beware that these kinds of fertilizers can have a detrimental impact on the environment. We just stick to high-quality compost for this reason.

There are several different ways you can spread the compost on your lawn, from using a shovel to hiring a compost blower. A rake is helpful to make sure the compost is settled on the soil rather than the grass.

Step 2: Spread the seed evenly over the entire lawn

The grass seed will come with instructions on how much seed to use. We suggest you follow this.

Some people recommend increasing the seed rate, but this is mainly to compensate for lousy preparation or aftercare, causing a significant % of the seeds to fail. If you follow all the other steps in this guide, then this won’t be an issue. Using too much seed will increase competition and make it harder for the grass to thrive.

Minimal wind and calm conditions are best for seed spreading. Too much wind will blow your seeds around, and you could end up with a very uneven lawn.

If you have a small lawn, then you can spread the seed by hand or with a rotary seed spreader.

Man using a rotary sprayer to spread grass seed
Rotary sprayers are small devices operated by hand

For larger areas, it’s better to use a drop spreader or a broadcast spreader.

Man seeding a lawn with a broadcast spreader
Broadcast seed spreaders can cover larger areas

Drop spreaders are very precise and good for seeding areas with lots of obstacles like flower beds. Broadcast spreaders are the most efficient spreader type and can seed an area 3-4 times their width.

Step 3: Water immediately after spreading the grass seed

Once you’ve finished seeding, water the lawn straight away. This will embed the seeds firmly into the layer of compost, giving them the best chance of sprouting.

Some people like to top-dress the seeds after spreading them, but usually, a light rake will be enough to make sure they’re well mixed into the compost. If you’ve aerated the lawn, then the seeds should quickly fall into the aeration holes.

Mixing your grass seed into the soil helps to protect it from birds and other animals that would otherwise eat it.

Step 4: Lawn care (irrigation and mowing)

The watering pattern is the most critical part of caring for a new lawn. The soil needs to be kept constantly moist. Lightly water the lawn twice daily until the seeds have germinated. This can take anywhere from a week to 3 weeks.

Once they’ve germinated start watering them more heavily every few days, enough to wet the top layers of soil. This will encourage them to set deeper roots.

Woman watering the lawn with a hose
Grass seedlings should be kept constantly moist

When your new grass blades have reached the same height as the established grass blades, or are over an inch high, then you can go back to a typical watering pattern. At this point, you can also start mowing your lawn again. Mowing before this point risks pulling the new lawn out completely.

You should also avoid weed treatments until the seeds are fully rooted. Weed killers can’t distinguish between grass seed and weed seed. Lawn insect killers are fine to use and won’t harm new grass.

In the long run, regular monitoring and maintenance will keep your lawn thick and full.

Choosing the right seed

Different grass seeds require different conditions to grow, so you need to choose the right one for the climate you live in. Grass seeds don’t come cheap, but you get what you pay for. Cheaper seeds are likely to be a mixture of different types of grass and may even contain weeds.

If your old lawn performed well in its prime, then it’s best to stick with a similar seed. Take a look at this guide if you don’t know your current grass type.

The best grass types for warm Southern climates are:

  • Bermudagrass
  • Zyosia grass
  • Centipedegrass
  • Bahiagrass

 

These grasses can withstand the extreme heat you find in the South, but won’t tolerate temperatures much below freezing.

The best grass types for colder Northern climates are:

  • Kentucky Bluegrass
  • Tall Fescue
  • Bentgrass
  • Perennial Ryegrass

 

These grasses are hardy enough to survive a long cold winter and will tolerate moderate temperatures in the summer.

Another consideration when it comes to picking a seed is how shady your lawn is. If lack of sunshine is a problem, then go for a shade-tolerant seed such as fine fescue.

Should I overseed my lawn?

Overseeding works best when over 50% of your lawn is healthy. If less than 50% of the lawn is healthy, you should consider completely returfing it. Also, if you only have a few bare spots, then spot seeding will be more efficient than overseeding, which involves the entire lawn.

When is the best time to overseed my lawn?

To ensure your new grass seed has the best chance of thriving, it’s important to sow it at the right time.

Best time to overseed a lawn in the midwest or northeast

Midwest and Northeast lawns tend to have cool-season grasses. The best time to overseed a cool-season grass is in early fall or late summer. To be more specific, aim to overseed at least six weeks before the first frost. The soil is moist and still warm enough to encourage seed germination, and the air is cool enough to support growth. Also, during these months there’s less competition from weeds.

The seeds will have time to germinate before the winter freeze halts growth, and then can develop a strong root system in the spring before the height of summer.

If you can’t overseed in the fall, spring is the next best time. However, soil moisture can be an issue so you’ll have to make sure you’ve got a solid irrigation plan in place.

Best time to overseed a lawn in the South

Warm-season grasses are grown in the South and need warm weather to survive. Therefore the best time to overseed these lawns is in late spring.

If you’re living in the South and are overseeding for winter colour, then wait until the night temperature falls below 65 degrees. It’s at this point your warm-season grass starts to struggle.

Best time to overseed a lawn in the West

If you live in the West, you can have either warm or cold season grass. Determine your grass type, if it’s a cool-season variety overseed in the fall, and if it’s a warm-season variety overseed in the spring.

Summary

That’s it for our guide on how to overseed a lawn.

Overseeding every year is good practice to maintain a healthy lawn and as a weed control measure. It’s also a great time to check the general health of the soil supporting your grass and make any adjustments you need.

Think of it as a spring clean for your lawn – except in the fall if you have cool-season grass.

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