The rates
| Purpose | Rate | A 100 m² lawn needs |
|---|---|---|
| New lawn from bare soil | 35-50 g/m² | 3.5-5 kg |
| Overseeding an existing lawn | 20-25 g/m² | 2-2.5 kg |
| Repairing bare patches | 50-60 g/m² | by patch area |
| Hard-wearing / family lawn mix | 40-50 g/m² | 4-5 kg |
| Fine ornamental lawn | 30-40 g/m² | 3-4 kg |
| Shade mix | 40-50 g/m² | 4-5 kg |
| Wildflower meadow | 1-5 g/m² | 100-500 g |
The wildflower figure is not a typo. Meadow mixes are sown at a fraction of lawn rates because the species are larger, slower and are meant to be sparse — sowing meadow seed at lawn rates wastes most of it and produces a lawn of weeds.
Why more seed makes a worse lawn
Grass seedlings compete for the same light, water and nutrients as each other. Sown too densely they grow tall and thin racing for light, produce weak root systems, and then thin out under the first drought or frost. What you get is a lawn that looked perfect for three weeks and then went patchy.
There is also a practical cost: seed is the expensive part of a lawn. Doubling the rate on 100 m² is another 2-3 kg of seed to achieve a worse result.
The opposite error is real too. Under 20 g/m² on bare soil leaves gaps that weeds fill before the grass closes over, and weeds are far harder to remove than they are to prevent.
What is in the bag changes the rate
- Ryegrass-heavy mixes
- Large seed, fast germination in 5-10 days, hard wearing. Fewer seeds per gram, so the rate by weight is at the higher end. The default for family lawns.
- Fescue-heavy mixes
- Fine seed, many more seeds per gram, slower to establish at 14-21 days. Lower rate by weight for the same seed count. Finer looking, less tolerant of traffic.
- Bentgrass
- Very fine seed, sown at 8-15 g/m². Ornamental and demanding; not a general-purpose choice.
- Shade mixes
- Usually fescue-based with added shade-tolerant species. Sow at the top of the range: establishment in shade is slower and losses are higher.
This is why bag rates differ from each other and from any table. The number on the bag accounts for the actual seed count of that mix, so where the bag and this guide disagree, follow the bag.
The soil under it
Seed rate is the last decision, not the first. Grass roots occupy the top 100 mm of soil, and no sowing rate compensates for sowing onto compacted subsoil.
- 100-150 mm of topsoil for a new lawn. Below that, roots hit the pan and the lawn browns off in the first dry spell.
- Rake to a fine tilth. Seed needs contact with soil, not to sit on lumps.
- Firm the soil before sowing, by treading or rolling. Loose soil settles unevenly afterwards and the lawn ends up wavy.
- Sow at 5-10 mm depth, or simply rake in lightly. Seed buried deeper than 15 mm will not emerge.
- Keep it damp, not wet, for the first three weeks. Letting the surface dry once after germination starts kills the seedlings outright.
- Sow half the seed walking in one direction and the other half at right angles. Sowing in one pass always leaves stripes.
Timing
| Season | Verdict | Why |
|---|---|---|
| Early autumn | Best | Warm soil, reliable rain, weeds slowing down |
| Mid spring | Good | Soil warming, but you are watering all summer |
| Early summer | Risky | Germination is fast but drought stress kills seedlings |
| Midsummer | Avoid | You will be watering twice a day and still lose it |
| Winter | Avoid | Soil below 8 °C, seed sits and rots or gets eaten |
Soil temperature matters more than the calendar: most lawn grasses need 8-10 °C to germinate. A cold spring pushes everything back by weeks regardless of the date.
A worked example
A new back lawn, 9 × 6 m, on ground that currently has 40 mm of poor topsoil over clay. Hard-wearing family mix.
area = 9 × 6 = 54 m²
seed = 54 × 45 g = 2 430 g → 2.5 kg
topsoil to add = 54 × 0.08 m = 4.3 m³
with 15% settlement = 5.0 m³
Two and a half kilos of seed and five cubic metres of topsoil — about six tonnes. The seed is the cheap part and the soil is the job. This is the usual shape of a lawn project, and it is why lawns fail: people buy the seed, skip the soil, and blame the seed.
Practical notes
- Weigh out the seed for a marked-out 10 m² and sow that, rather than eyeballing across the whole lawn. Hand-sowing without a reference is always uneven.
- Mix the seed with dry sand to make it easier to see where you have been and to spread small quantities evenly.
- Net or fleece the area if birds are a problem. They can take a significant share of a surface sowing in a day.
- Do not use weed-and-feed or any residual herbicide before sowing. Many prevent germination for weeks or months.
- First cut when the grass reaches 60-70 mm, on the highest mower setting, with sharp blades. Cutting too early or too short pulls the seedlings out by the roots.
- Buy seed for the current season. Germination rate drops noticeably after two years of storage.