If your lawn isn’t looking as thick and healthy as you’d like, overseeding can be the perfect solution. It’s economical and easy – as long as you know what you’re doing.
Get it wrong, though, and you can find you’ve spent time and energy to no avail. We’re here to make sure that doesn’t happen!
Just follow our guide to how to overseed a lawn. We’ll take you through the process step by step, and share some great tips to get professional results. So if you’re ready, let’s get started!
Tools for overseeding a lawn
- Garden fork or lawn aerating shoes
- Lawn fertiliser
- Bucket (or wheelbarrow, if your lawn is very large)
- Lawn topdressing
- Grass seed
- Rake or broom
- Sprinkler or hose with a fine spray nozzle
How to reseed a lawn
Step 1: Make sure your lawn is ready for overseeding
Before you get started, make sure your lawn is in the best possible condition for new grass seed. Ideally, you will already have scarified it, removing thatch and moss.
If you haven’t scarified before, there are plenty of guides online to how to do it. If you’ve got a mechanical scarifier, it will require a lot less effort. But for smaller lawns, a wire toothed rake will work just as well. This guide from BBC Gardener’s World gives you a helpful overview of both techniques.
Step 2: Mow your lawn
If you’ve already scarified your lawn, you’ll probably have mown it first. But if not, now’s the time to get out the lawnmower. The shorter grass will help you see what you’re doing. And it will give the new grass seed the best chance of reaching the surface of the soil.
Take your grass down to a height of about 25mm if you can. But if your lawn is a lot longer than this, don’t cut too far. It will be too much of a shock to the grass and it will struggle to repair itself. A good rule of thumb is to never cut off more than a quarter to a third of the green part in one go.
Pro tip: Sharpen your lawnmower blade after every 25 hours of use. That will ensure it slices cleanly through the grass, avoiding shredded edges that are vulnerable to disease and pests.
Step 3: Spike the lawn
Spiking the lawn helps air get into the soil, creating better conditions for both existing grass and new seed.
To do this, you’ll need your garden fork. Dig the tines into the soil to a depth of about 150 mm. Do this every 300 mm or so across the surface of your lawn. This YouTube video from Deco Bliss shows you how to do it.
You can also buy special lawn aerating shoes. These strap onto your normal shoes, allowing you to spike the lawn as you walk. They’re not expensive, and they considerably reduce the effort involved.
Step 4: Fertilise the lawn
If your lawn hasn’t been fertilised in the last four months or so, give it a feed before you overseed. This will add nutrients that will be welcomed by both existing grass and new seeds. But it does need to be done a few days ahead of when you want to overseed.
Three to four days in advance will be fine for most general purpose fertilisers. Even better, choose one that’s specially formulated for pre-seeding. Follow the instructions on the packaging carefully, and take your time to get even coverage.
Take care, though, not to use any products that contain weedkillers. These can remain in the soil for several weeks and will harm the grass seed.
Step 5: Mix your grass seed with lawn topdressing
A few days after fertilising, it’s time to sow your grass seed. The quickest and easiest way to do this is to mix it in with your lawn topdressing.
You can buy topdressing ready-made, or mix up your own. If making your own, a mixture of two parts sand, two parts topsoil, and one part compost works well in most conditions. Just make sure that the sand you use is sharp sand, and that it’s lime-free.
Check the instructions on your grass seed to see how densely you should sow it. Make sure you use the measurement for overseeding, rather than for laying a new lawn. Then measure out the right amount of seed for your lawn and mix it thoroughly with the topdressing.
For most lawns, you’ll be able to do this in a bucket. But if you’re lucky enough to have a very large green space, you may need a wheelbarrow instead.
Pro tip: Go easy on the amount of topdressing you use! If in doubt, err on the side of caution. If you use too much, you’ll bury the grass you have already. And without light, it will quickly die.
Step 6: Apply your seed and topdressing mix
Walk at a steady pace across the surface of your lawn, sprinkling the grass seed and topdressing mix as you go. You want to get as even coverage as you can. For most grass seed mixtures, you’ll be aiming to sow between 10 and 20 seeds over every square inch of lawn.
Don’t be tempted to use more than the instructions say! The seeds need enough space to germinate. And grass growing too densely can cause the roots to rot, especially if it’s damp.
Pro tip: Hold your hand about 18 inches above the ground as you drop the seed. That will help you spread it evenly and lessen the chance of any breezes sending it off course.
Step 7: Rake over the ground
You want to make sure the seeds get to the surface of the soil rather than resting on the existing grass. To help make sure that happens, get out your rake or a broom.
Drag the flat side gently across the grass. You don’t need to apply any downward pressure. Your aim here is to knock the seeds off any blades of grass so that they make contact with the earth.
Walk up and down methodically, making sure you cover every part of the lawn surface.
Step 8: Water the lawn
Your new seeds need moisture in order to germinate. If it doesn’t rain within a couple of days of overseeding, water your lawn by hand. A sprinkler is ideal if you have one. That will allow a light spray of water to be distributed over the lawn over a longer period.
But if you don’t have a sprinkler, don’t worry. You can use a hose with a fine spray pattern, or even a watering can with a fine rose.
Pro tip: Keep watering the grass regularly over the first two to three weeks after sowing the seed. That will maintain good moisture levels in the soil and speed up new growth.
- The whole process of overseeding a lawn takes several days, so plan ahead. Remember that you’ll need to cut and scarify your lawn first. And you’ll need to wait at least three days after fertilising before sowing the seed.
- It’s also a good idea to check the weather forecast. It’s best to overseed the day after rain. And if it rains after you’ve sown the seed too, it’ll save you having to water your lawn by hand.
Tackling bare patches
- The odd bare patch in your lawn can be tackled without having to overseed the whole thing. For small areas, use a dining fork to scrape over the surface of the soil. Then sow the seed at the same rate recommended for new lawns, and lightly water it in.
Protect young grass as it grows
- Avoid walking on new grass while it’s getting established. Try to keep off it for at least the first week, and ideally for three weeks.
- If you don’t have a hose or sprinkler that can reach over the whole area without stepping on it, lay boards over the grass. That will help to distribute your weight more evenly as you walk.
- You may also want to protect the seeds from birds, for whom they will be a tasty snack! Laying a fine mesh over the surface of the grass works well. Another option is to thread old CDs or foil containers along a string, and hang that over the lawn. It makes an effective scarecrow.
Take care with the first few cuts
- Mowing your lawn is good for its health, but don’t go too low. For the first two or three cuts after overseeding, increase your cutting height to about 50 mm. You can then reduce it gradually down to 25mm over the next few cuts.
- You can mow an overseeded lawn as often as you would normally. But remember, never cut off more than about a quarter of the blade of grass with each cut.
Time to overseed that lawn!
We hope we’ve given you all the information you need to successfully overseed your lawn! Take the time for proper preparation, including scarifying, aerating and fertilising the soil. Mix your seed with a good topdressing and apply at the correct rate. And pay attention to aftercare.
Do all of that, and your reward will be a thick, healthy lawn that will have visitors to your garden green with envy.
Feel free to leave any questions you have in the comments section. And if you’ve overseeded your lawn, please let us know how you got on!