How to sow a lawn step by step (and when to do it)

Sowing a lawn is cheap and, done at the right time, works out almost every time. The difference between a lawn that germinates dense and even and one full of bare patches comes down to two things: ground preparation (70% of the success) and the watering of the first three weeks. Seed and timing help, but poorly levelled ground or a watering that fails for two days in a row will ruin the best mix.

This guide covers when to sow for your climate; how to prepare the ground step by step; which seed mix to choose for the use and exposure; the right rate and how to spread it evenly; the first watering and the watering calendar up to germination; and the care of the first six weeks up to the first cut. Ten FAQs at the end.

When to sow

Lawn seed germinates when the soil is between 12 and 20 °C with constant moisture. That leaves two windows a year:

• Autumn (mid-September to mid-October): the best time. The soil is still warm, rain helps with watering, few weeds are germinating and the lawn has all autumn, winter and spring to establish before its first summer.
• Spring (April to mid-May): second choice. It works, but you compete with seasonal weeds and the young lawn reaches summer with little root, so you have to water a lot.

Avoid sowing in high summer (it dries out before germinating) and in winter (it won't germinate and the seed rots or is eaten by birds).

Preparing the ground (step by step)

1. Clear the surface: remove stones, roots, debris and all existing vegetation. If there are many perennial weeds, deal with them weeks in advance.
2. Loosen it: rotavate or fork over the top 15-20 cm. Compacted soil won't let the root go down and water pools.
3. Amend: spread 3-5 cm of compost or mature leaf mould and mix it into the soil. On clay, also add coarse river sand; on sandy soil, more organic matter. See how to identify and improve it in types of garden soil.
4. Level: with a levelling rake, leave the surface smooth and with a slight slope (1-2%) so water drains away from the house. Fill the hollows: any dip becomes a puddle and a bare patch.
5. Firm it lightly: roll with a half-filled water roller or tread with boards. Leave the soil firm but not packed: if you sink more than 1 cm when walking, it needs more firming.
6. Wait 1-2 weeks and remove the first flush of weeds that germinate. Rake the surface very lightly again before sowing.

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Which seed to choose

Buy seed with a recent packing date (it loses germination power over the years) and avoid very cheap mixes: they usually contain too much annual ryegrass, which germinates fast and looks good but disappears within a year.

Sowing and covering

1. Rate: between 25 and 40 g per m² depending on the mix (it's on the bag). More is not better: excess seed competes with itself and comes up weak.
2. Even spread: divide the seed into two halves. Sow the first walking one way (say, north-south) and the second at right angles (east-west). A spreader makes it easier; by hand, mix it with dry sand so you can see it better.
3. Cover: rake very lightly to bury the seed 0.5-1 cm, or spread a very thin layer (2-3 mm) of sieved leaf mould over the top. Seed left on the surface is eaten by birds or dries out.
4. Firm again lightly with the roller so the seed makes good contact with the moist soil.

Watering: what decides everything

From sowing until the grass is 3-4 cm tall, the soil cannot dry out for a single day:

• Weeks 1-3: water 2-4 times a day, a little each time, just enough to keep the top 2 cm moist. In heat or wind, more often. A single dry day kills the germinated seed.
• Weeks 3-5: when most has germinated, switch to one watering a day, a bit longer, so the root starts to go down.
• From week 6: normal established-lawn watering: few long, spaced-out soaks.

Use fine-droplet sprinklers or a mist nozzle: a strong jet washes the seed away and creates channels and bare patches.

The first six weeks

• Don't walk on the new lawn until the first cut. If you must cross it, put down boards.
• First cut: when the grass reaches 8-10 cm, and only if the soil is firm (not muddy). Cut just the tip, leaving it at 5-6 cm, with a well-sharpened blade. Collect that first clipping.
• Bare patches: at 3-4 weeks the thin areas are already visible. Scratch the surface a little, sprinkle seed, cover with leaf mould and water. The sooner, the better.
• First feed: 4-6 weeks after germination, a gentle starter fertiliser (high in phosphorus) or a slow-release one at half rate.
• Weeds: pull by hand the ones that appear. Don't use selective weedkillers until after the 3rd or 4th cut.

Quick glossary

• Seeding rate: grams of seed per m²; 25-40 g/m² for a new lawn, 15-25 g/m² for overseeding.
• Staggered germination: some species in the mix coming up before others (ryegrass in 5-7 days, fescue and meadow grass in 14-21); it's normal, don't reseed too soon.
• Germination rate: the percentage of viable seeds in a batch; it drops over the years, which is why recently packed seed matters.
• Annual ryegrass: a very fast-germinating species that pads out cheap mixes but disappears in one season; different from perennial ryegrass, which stays.
• Hard-wearing mix: a blend of traffic-tolerant grasses (perennial ryegrass, tall fescue, meadow grass) for family use.
• Top dressing: a thin layer of leaf mould or sand and sieved compost spread to cover the seed and level the surface.
• Turf (sod): already-grown lawn laid in slabs; instant but 10-15 times more expensive than sowing.
• Overseeding: sowing over an existing lawn to thicken it, after mowing low and scarifying.

Frequently asked questions

How long does lawn seed take to germinate?

Between 7 and 21 days depending on the mix and temperature. Ryegrass shows in 5-7 days; fescue and meadow grass take 14-21. As mixes contain several species, you'll see staggered germination over 2-3 weeks: that's normal, don't reseed too early.

Is it better to sow a lawn or lay turf?

Turf gives an instant lawn and can be laid almost all year, but it costs 10-15 times more and the choice of species is limited. Sowing is much cheaper, has more mix variety and, done well, looks just as good; you just have to wait 2-3 months and take great care with the early watering.

Can I sow lawn seed over my existing lawn to thicken it?

Yes, it's called overseeding. Mow very low, scarify to open the soil, spread seed (20-25 g/m²), top-dress with a thin layer of leaf mould and water daily for 2-3 weeks. It's the best way to recover a thin lawn without starting over.

What seeding rate do I need?

The one on the bag, usually 25-40 g per m² for new sowing and 15-25 g/m² for overseeding. For 100 m² of new lawn, between 2.5 and 4 kg. Go a bit heavier on the edges and traffic areas.

Why did I get bare patches after sowing?

The most common causes: the soil dried out for a day during germination, the seed was spread unevenly, water pooled in a poorly levelled dip, or birds ate the seed left on the surface. Scratch, reseed, cover with leaf mould and water.

Do I need to put new soil on top of the seed?

No new soil is needed, but the seed should be covered: a light pass of the rake to bury it 0.5-1 cm, or a very thin layer of sieved leaf mould. What matters is that the seed isn't left exposed or buried more than 1 cm.

Can I sow a lawn in spring?

Yes, from April to mid-May. It germinates well, but you'll have more weed pressure and the young lawn reaches summer with little root, so be ready to water a lot. If you can choose, autumn is the better time.

When can I walk on and use the new lawn?

Light use, after the 2nd or 3rd cut (about 8-10 weeks). For intense play by children or pets, wait until the end of the first full season, when the root is deep and the lawn has tillered.

Do I need a roller to sow a lawn?

It helps a lot: it firms lightly so the seed contacts the moist soil and levels small irregularities. You don't need an expensive one; water-filled types work well and many garden centres hire them out.

What do I do if it rains hard right after sowing?

Gentle rain is ideal. A downpour can wash the seed away and form channels: when it clears, redistribute the seed that has piled up at the edges towards the bare patches, rake very lightly and carry on with normal watering. That's why it pays to cover the seed well when sowing.

What's the best time to sow a lawn?

From mid-September to mid-October in most temperate areas: the soil is still warm, rain helps and there are few weeds. In a wet, mild region the spring window (April) also works well. In a hot, dry climate, always sow in autumn and skip spring because of the early heat.

Can I sow lawn seed without removing the grass I already have?

Yes, it's overseeding: mow very low, scarify to expose soil, spread 15-25 g/m² of seed, top-dress with a thin layer of leaf mould and water daily for 2-3 weeks. It recovers a thin lawn without the work of starting over. If more than half is bare or weeds, better to redo it entirely.

Once the new lawn is established, keep it up with how to care for a lawn, and if bare or yellow patches appear, with a patchy, dry or yellow lawn.