How to Prepare your Lawn for Seeding

Can you just scatter grass seed on your lawn and hope for the best? Technically, yes. Will it work? Probably not very well.

Grass seed needs three things to germinate: moisture, warmth, and good contact with the soil. Throw seed onto compacted ground, thick thatch, or lumpy soil and most of it will fail. Birds will eat some. Rain will wash some away. The seeds that do germinate will struggle to put down roots.

Proper preparation takes a bit of effort, but it’s the difference between patchy disappointment and a lawn you’re actually proud of. Here’s how to do it properly.

New Lawn vs Overseeding: Different Approaches

Before you start, it helps to know which situation you’re dealing with – the preparation is quite different.

Starting a new lawn from scratch (bare soil, building site, removed turf): You’ll need to work the soil deeply, improve drainage if necessary, and create a completely new seedbed. This is more work but gives you a blank canvas.

Overseeding an existing lawn (thin patches, worn areas, thickening up): You’re working with what’s already there. The goal is to create pockets where new seed can establish among the existing grass. Less disruptive but requires different techniques.

We’ll cover both approaches below.

Preparing a New Lawn from Bare Soil

If you’re starting from scratch – perhaps after building work, removing old turf, or creating a lawn where there wasn’t one – here’s the process:

1. Clear the Area

Remove all debris, rubble, large stones, and any vegetation. If there are existing weeds, deal with them now – it’s much harder once grass is established. For persistent weeds like couch grass or bindweed, you may need to spray with glyphosate and wait 2-3 weeks before proceeding.

2. Dig or Rotavate

The soil needs to be loosened to a depth of at least 15-20cm. This breaks up compaction and allows roots to penetrate. For small areas, a garden fork works fine. For larger lawns, hire a rotavator – it’ll save your back and do a better job.

While you’re digging, remove any roots, large stones, and debris that come to the surface.

3. Improve the Soil (If Needed)

This is the time to address any soil problems:

Heavy clay: Add sharp sand or grit to improve drainage. Work it into the top 10-15cm.

Sandy soil: Add organic matter to help retain moisture and nutrients.

Poor soil: If your soil is thin, stony, or low quality, you may need to import topsoil. Aim for at least 10-15cm of good quality screened topsoil over the existing ground.

A note on compost: Well-rotted compost is excellent for improving soil structure, but don’t use it as a top layer for seeding. It’s too lumpy and often too rich for young grass seedlings. Dig compost into the soil a few weeks before seeding, then top with fine topsoil or rake to a fine tilth.

4. Level and Firm

Rake the area to create a level surface, breaking up any lumps as you go. Remove stones larger than a marble – they’ll cause problems later.

Once level, firm the soil by treading it systematically (shuffling across in rows) or using a light roller. This removes air pockets and prevents the soil settling unevenly after seeding. Then rake again lightly to create a fine, crumbly surface – what gardeners call a “fine tilth.”

The surface should be firm enough that you don’t sink in more than about 1cm when walking on it, but loose enough on top that a rake moves through easily.

5. Final Rake and Wait

Ideally, prepare your seedbed a week or two before sowing. This allows the soil to settle naturally and – importantly – lets any weed seeds germinate. You can then hoe off these weeds before sowing your grass, giving your lawn a head start.

Preparing an Existing Lawn for Overseeding

If you’re thickening up a thin lawn or filling bare patches, the approach is different. You need to create conditions where new seed can reach the soil and establish alongside existing grass.

1. Mow Short

Cut the existing grass shorter than usual – around 2-3cm. This reduces competition for light and allows seed to reach the soil surface. Collect the clippings.

2. Scarify

This is the key step. Scarifying (or raking vigorously) removes the layer of dead grass, moss, and debris (thatch) that builds up at the base of the lawn. Thatch prevents seed from reaching the soil.

Use a spring-tine rake and really work it into the lawn – it should feel quite aggressive. For larger areas, hire a powered scarifier. You’ll be amazed (and slightly horrified) at how much material comes out.

If your lawn has significant moss problems, treat the moss first and let it die back before scarifying. Raking out live moss just spreads it around.

3. Aerate (Optional but Helpful)

If your soil is compacted – common on heavy-use lawns – aeration helps. Push a garden fork into the soil every 10-15cm across the area, or use a hollow-tine aerator for better results. This improves drainage, allows air to the roots, and creates pockets where seed can settle.

4. Top-dress (Optional)

For lawns in poor condition, spreading a thin layer (5-10mm) of fine topsoil or lawn top-dressing over the surface after scarifying helps level minor bumps and provides a good seedbed. Work it into the grass with a rake or stiff brush.

Sowing the Seed

With your seedbed prepared, sowing is straightforward:

Check the sowing rate. Most grass seed mixes recommend 35-50g per square metre for new lawns, less for overseeding. More isn’t better – overcrowded seedlings compete with each other and produce weak grass.

Divide and conquer. Split your seed in half. Sow the first half walking in one direction across the area, then sow the second half walking at right angles. This gives more even coverage than trying to do it all in one pass.

Rake in lightly. The seed should be barely covered – no more than 5mm of soil. Grass seed needs light to germinate, so don’t bury it. A light rake over the surface is enough, or you can simply tread it in gently.

Water immediately. Give the area a thorough but gentle soaking. Use a fine spray – heavy water flow will displace seeds and create bare patches.

After Sowing: The Critical Period

The next few weeks are make-or-break. Your seeds need consistent moisture to germinate – if they dry out, they die.

Water daily (twice daily in hot weather) until germination, keeping the top few centimetres of soil moist but not waterlogged. Use a fine spray to avoid disturbing the seeds.

Most grass seed germinates within 7-14 days, depending on the mix and soil temperature. Keep watering regularly until the grass is well established and you’ve mowed it a few times.

Avoid walking on newly seeded areas until after the first mow. Young grass is fragile and easily damaged.

When to Prepare and Sow

Timing matters. Grass seed needs warm soil to germinate – ideally above 10°C consistently.

Spring (late March – May): Soil is warming up, moisture is usually reliable. Good conditions for germination, and grass has the whole growing season to establish before winter.

Autumn (September – mid October): Often the best time. Soil is warm from summer, cooler air reduces water stress, and autumn rain provides natural irrigation. Grass establishes well before going dormant for winter.

Summer: Possible but risky. Hot, dry conditions stress young seedlings. You’ll need to water religiously, sometimes twice daily. Not ideal unless you’re prepared for the commitment.

Winter: Not recommended. Soil is too cold for germination and seeds may rot. If you must sow, dormant seeding in late winter (February) can work – seeds sit dormant until spring warmth triggers germination.

For detailed guidance on timing, see our guide to when to put down grass seeds.

What About Covering the Seed?

You don’t have to cover grass seed, but it can help in certain situations:

Bird protection: If pigeons or sparrows are a problem in your garden, they’ll treat your seedbed as a buffet. Lightweight netting or horticultural fleece keeps them off without blocking light or rain.

Moisture retention: Clear horticultural fleece helps retain soil moisture and slightly raises soil temperature, which can speed germination. Remove it once grass is up.

Steep slopes: On sloping ground where seed might wash away, a light covering of straw or fleece helps hold everything in place until grass establishes.

For most flat lawns in typical British conditions, covering isn’t necessary if you’re watering regularly.

Frequently Asked Questions

Can I just throw grass seed on my lawn?

You can, but results will be poor. Seed needs contact with soil to germinate properly. At minimum, rake vigorously to remove thatch and create some bare soil, then water consistently. Proper preparation gives much better results.

Do I need to use topsoil?

For new lawns on poor soil, yes – you need at least 10-15cm of decent topsoil. For overseeding existing lawns, a thin top-dressing can help but isn’t essential if you scarify properly. Always use screened topsoil, not compost, as the top layer.

Why not compost instead of topsoil?

Compost is lumpy and often too nutrient-rich, which can burn young grass seedlings. It’s excellent dug into soil to improve structure, but topsoil is better as a seedbed surface. If using compost, dig it in a few weeks before seeding and top with fine topsoil.

How long after preparing should I sow?

Ideally, wait 1-2 weeks. This lets the soil settle and allows weed seeds to germinate so you can remove them before sowing grass. If you’re in a hurry, you can sow immediately after raking to a fine tilth.

What’s the best grass seed for a new lawn?

It depends on your conditions. Ryegrass-dominant mixes establish quickly and handle wear well – good for family lawns. Fescue mixes tolerate shade and drought better. For shady gardens, choose a shade-tolerant blend. See our grass seed range for options suited to different situations.

The Bottom Line

Preparing your lawn for seeding isn’t complicated, but it does require some effort. Clear the area, loosen the soil, level and firm, create a fine surface, then sow and water. The extra hour or two spent on preparation pays off massively in germination rates and the quality of your finished lawn.

Skip the preparation and you’ll spend months trying to fill in patchy areas that should have grown first time. Do it properly and you’ll have a lawn worth looking at.

For more seeding guides and lawn care advice, explore our UK lawn care hub.

Seedbed ready? Browse our grass seed collection to find the right mix for your lawn – from fast-establishing ryegrass to shade-tolerant blends for tricky spots.