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A gorgeous green lawn is the pride and joy of many homeowners. 

There’s a sense of satisfaction when looking out and seeing a lush lawn that you’ve worked so hard on. But when bare patches start showing up, it’s not so pleasant.

If you have dead grass or barren spots, you can fix things by overseeding – the process of adding grass seed to existing lawn without turning topsoil.

How to overseed a lawn? Start by mowing the grass, then amending the soil. Spread grass seed to the correct density and fertilise the lawn afterwards. Lastly, water regularly for a few days to help grass seed germination.

Keep your lawn healthy with essential maintenance, including overseeding. You just need the right tools, good timing, and a little elbow grease.


What is Overseeding?

Overseeding is the process of spreading grass seed over existing lawn to fill in bare patches or fill out thin lawns. It’s different from reseeding, which involves uprooting lawn grasses and starting from scratch.

Can you seed over existing grass? Not really – if your lawn is healthy and thriving, there’s no need to overseed. It’s best to seed over thin, patchy areas to restore lawn health.


Why Overseed Your Lawn?

Garden with fresh green grass both shrub and flower front lawn

There are several benefits to spreading new grass seed onto your lawn, such as:

  • Thicker grass growth
  • Improved lawn health
  • Fewer weeds
  • Filled-in thin or bare patches
  • Health boost in winter


When to Overseed a Lawn

The best time to overseed lawn is when it’s most active and growing. 

This will depend on the type of turf on your lawn – whether you planted warm-season grass or cool-season grass.


When to overseed warm-season grasses

A warm-season lawn is most active in late spring to late summer. 

Common warm-season grasses in Australia are Couch, Kikuyu, Buffalo, and Zoysia.

If you need to overseed a warm-season lawn, do so in late spring or early summer. The soil temperature should ideally be between 21–30ºC.


When to overseed cool-season grasses

For a cool-season lawn, the period of activity and growth is spring and autumn. 

Some common cool-season grasses in Australia are tall fescue, Kentucky bluegrass, and ryegrass.

Overseed a cool-season lawn in late summer or early autumn – at least 45 days before any frost is expected in your area. Soil temperature should be between 10–15ºC.

You can overseed a cool-season grass lawn in spring, but there may be more weeds that compete with new grass. 

Do not overseed in early spring since it will be too cold.


How often to overseed your lawn

It will depend on the needs of your own lawn. 

If your lawn thins out over winter or the rainy season, then you should overseed around once a year. 

Most lawns, however, will usually need overseeding every few years.


a handful of grass seeds


Before Overseeding Your Lawn

For new lawn seed to establish and grow, it needs to reach the soil. 

If you have a noticeable layer of thatch, then you will need to dethatch your lawn before overseeding. 

After that, it’s also advisable to aerate your lawn if you haven’t in the past year.

You may also consider levelling your lawn if there are bumps, dips, or slopes. It’ll make it easier to seed and mow the yard in the long run.


How to Overseed a Lawn

Once you’ve prepped your lawn and chosen the appropriate grass type for the seeds, it’s time to overseed your lawn. 

There’s no real “best grass seed” for overseeding – it will depend on your existing type of grass and local conditions.


1. Mow the existing grass

Start up your lawn mower – it’s time to cut grass blades! 

Mow the lawn down to around 3.0cm, or as short as you can manage without scalping the turf. 

Rake away any dead grass and grass clippings afterwards, as well as sticks, rocks, and other debris.

If you regularly work with a professional lawn mower, make sure they know how low to go!


2. Amend your soil

Check if your soil has the essential nutrients for growth. You can conduct a soil test to check the type and pH. 

If the soil is too acidic or alkaline, you may need to amend the ground to balance it out. Meanwhile, peat moss, compost, and other organic material can improve soil nutrients.

Gardeners can also spread a thin layer of enriched topsoil to help the grass seed grow. If your seed mixture already contains topsoil, this step isn’t necessary.

Water the lawn lightly afterwards to moisten the ground.


3. Sow the grass seed

seeding lawn using a seed spreader

Load the grass seed into a seed spreader and get working! 

Seed density will depend on the thickness of your existing lawn and the type of seed you’re using. 

Use a grass type that suits your local climate and complements the established grass.


4. Feed the grass seeds

Apply fertiliser next, in whatever form you prefer. 

Lawn starter fertiliser is recommended, since it’s formulated for new grass. Avoid herbicide-type fertilisers since these could kill off the germinating seeds.

You can choose to mix up seed types to increase your lawn’s tolerance of drought, heat, cold, and foot traffic. However, make sure to use seeds within the same seasonal tolerance.


5. Water the lawn

How to water lawn after overseeding? Soak deeply right after spreading grass seed and fertiliser to soak the soil through and let the seeds settle. 

Then for the next several days, do some light waterings to keep the soil moist while the seeds germinate.

TIP: The best time to water a lawn is in the early morning, so water doesn’t evaporate as quickly. Avoid watering in the late afternoon or early evening since moisture left on grass blades could cause fungal diseases or rot.


Tips for Overseeding a Lawn

Don’t overseed your lawn before or after any heavy rain. The rainfall could wash away the seeds or waterlog the ground.

When to mow the lawn after overseeding? Not until the new grass reaches 3.0–5.0cm in height. 

And if you’re wondering how long to stay off the lawn after overseeding – around 3–6 weeks so you don’t compact the soil or crush the fresh grass.

Knowing how to overseed a lawn will keep away bare spots, and keep your lawn green and healthy. Then you can smile brightly as you look out onto the front of your house and see all that beautiful green growth.

About Author

Jamie Donovan

Jamie is an Australian horticulturalist and landscape designer. He enjoys writing about landscape architecture, garden design and lifestyle topics.


About Author

Jamie Donovan

Jamie is an Australian horticulturalist and landscape designer. He enjoys writing about landscape architecture, garden design and lifestyle topics.