Sowing a lawn: new lawn and overseeding done right
Whether you are creating a completely new lawn or filling gaps in an existing one, three things decide the result when sowing: the timing, the preparation of the soil and the care in the first weeks. The seed itself matters too, but good seed on poorly prepared soil achieves little. Here you can read when it is best to sow, how to proceed step by step and what counts after sowing.
In short
- The best time is late August to late September. Spring works too, as soon as the soil stays above about 10 °C.
- New lawn: about 25 g/m², overseeding: about 10 to 20 g/m², depending on how patchy the lawn is. Follow the manufacturer's rate.
- Work the seed in shallowly, no deeper than 0.5 cm, then roll.
- Keep the surface moist until everything has germinated.
- Before overseeding, mow as short as possible, aerate and top-dress with sand.
New lawn or overseeding?
| New lawn | Overseeding | |
|---|---|---|
| When it makes sense | lawn dead over large areas, moss and weeds dominate, soil open after building work or heavily compacted | individual bare patches, thin areas after winter or a dry summer, generally sparse sward |
| Effort | high: prepare the soil completely | low to medium: the existing sward stays |
| Seed rate | about 25 g/m², up to 30 g/m² for very early or late sowing | about 10 to 20 g/m², depending on the gaps |
| Usable | normal use after about three months | usually after a few weeks |
In most gardens, overseeding is enough. As long as there is still a closed sward of useful grasses, digging over is not worth it. Only when moss, weeds or weed grasses dominate, or the soil needs fundamental improvement, is a new lawn the better way.
The right time
Lawn grasses germinate from about 8 to 10 °C soil temperature, but quickly and evenly only at 14 to 25 °C. What matters is the temperature in the soil, not in the air. And the soil follows the air with a delay of several weeks.
| Period | Rating | Why |
|---|---|---|
| Late August to late September | ideal | warm soil, more dew and rain, little weed competition, enough time to root before winter |
| Early to mid October | possible in mild areas | only as long as the soil stays above about 10 °C |
| Late April to June | good | the soil warms up, but weeds germinate at the same time and the first dry spell often comes early |
| High summer | difficult | seedlings dry out quickly, only with very consistent watering |
| November to March | unsuitable | soil too cold, no germination |
Why late summer is usually better than spring is explained in detail in Why September is the best month for lawn renovation.
Which seed?
Good lawn seed is a mix of several grass species. Each brings different strengths. Which mix fits depends on light, soil, use and cutting height.
| Grass species | Strengths | Typical use |
|---|---|---|
| Perennial ryegrass (Lolium perenne) | germinates quickly, hard-wearing, robust | utility and play lawns, overseeding |
| Smooth-stalked meadow grass (Poa pratensis) | forms runners, closes gaps for good, resilient | utility lawns, sunny sites |
| Red fescue (Festuca rubra) | fine-leaved, tolerates shade and drought | ornamental lawns, partial shade, dry soils |
| Supina bluegrass (Poa supina) | very shade-tolerant, likes moisture | areas under trees, north sides |
| Bentgrass (Agrostis) | very fine, tolerates very low cutting | closely mown areas, golf greens |
Look for mixes made of named turf varieties rather than cheap forage grasses. For overseeding, the mix should match the existing sward, otherwise you end up with a patchy look made of different grass types. You can find mixes for different sites at our partner Mein Schöner Rasen.
Good to know
If you mow short with a reel mower, you benefit from fine-leaved grasses that tolerate a low cut, such as red fescue, smooth-stalked meadow grass and bentgrass. Coarse forage grasses in cheap mixes quickly become patchy when cut short.
A new lawn step by step
1. Prepare the soil
- Remove the old sward, weeds, roots and stones.
- Loosen the soil to a depth of about 10 to 15 cm.
- Improve heavy, loamy soils with sand, and poor sandy soils with some compost.
- Check the pH. Lawns do well at about 5.5 to 6.5. Lime clearly acidic soil.
- Rake to a fine tilth, level and roll lightly. Then leave for one to two weeks and level again so the soil can settle.
2. Sow
About 25 g per square metre, up to 30 g for very early or late sowing. More is not better: seedlings that stand too close compete for light and water and become susceptible to disease. Spread half the amount lengthways and the other half crossways so there are no stripes. On larger areas a spreader helps.
3. Work in and press down
Grass seed does not belong deep in the soil. Rake it in lightly or work it in with a drag mat so that it lies no deeper than about 0.5 cm. Then roll. Soil contact matters more for even germination than a covering.
4. Keep moist
Until all grasses have germinated, the surface must not dry out. Depending on the mix, that takes three to four weeks. During this time, give small amounts several times a day with a fine spray rather than a lot rarely, otherwise the water washes the seed away. Once the grass is up, gradually switch to watering less often but more deeply. More on this in Watering your lawn.
5. The first cut
Make the first cut with a sharp rotary mower when the grasses are about 6 to 8 cm high, taking off just over a third. Then lower the cutting height step by step over several cuts to your target height. Only use a reel mower once the sward has closed and there is no more sand or grit on the surface, otherwise the reel suffers. Do not scarify in the first few months.
Overseeding step by step
When overseeding, what matters is that the seed gets through the existing sward down to the soil and receives light there.
- Mow as short as possible and remove clippings and thatch thoroughly. The seedlings then get light and are not overgrown by the existing lawn.
- Aerate: pull out soil cores with spoons. This relieves compaction and creates holes in which seed germinates in shelter.
- Top-dress with sand: spread washed quartz sand and distribute it with the levelling rake. The sand fills the holes and evens out bumps.
- Overseed and work in: spread the seed, work it in with the drag mat and roll. Then keep moist as with a new lawn.
More on the individual steps in Lawn aeration and Top-dressing your lawn with sand.
Difficult sites
| Site | What helps |
|---|---|
| Shade | mixes with red fescue and supina bluegrass. Under very dense canopies, such as beech or spruce, a dense lawn will still not grow in the long run. |
| Loamy, compacted soil | aerate and top-dress with sand before sowing. Wet hollows quickly lead to seedling losses. |
| Sandy, dry soil | drought-tolerant grasses such as red fescue. Still water consistently during germination. |
| Slope | work the seed in well and water with a fine spray so it is not washed away. |
Common mistakes
| Mistake | Better |
|---|---|
| Sowing too early in spring | wait until the soil stays above about 10 °C |
| Burying the seed too deep or covering it thickly with soil | rake in shallowly, no deeper than 0.5 cm, and roll |
| Too much seed | stick to the manufacturer's rate, about 25 g/m² for a new lawn |
| Letting the germination phase dry out | keep moist continuously for three to four weeks |
| Overseeding into tall, dense grass | mow short first, remove thatch, aerate |
Frequently asked questions
How long does germination take?
Perennial ryegrass appears after 7 to 10 days in warm soil. Smooth-stalked meadow grass needs two to four weeks. It usually takes three to four weeks until a mix is fully up.
When can I walk on the new lawn?
For mowing and watering after about four to six weeks. A newly sown lawn can take normal use after about three months.
What if germination is patchy?
Wait first, slow-germinating grasses still come up after three to four weeks. If gaps remain, overseed there and check beforehand whether the spots are too wet, too dry, too shady or compacted.
Can I overseed in summer?
Possible, but risky. The seedlings dry out quickly. If you cannot water every day, it is better to wait until late August.
Tools for overseeding
- Lawnpecker: aerating with spoons before overseeding.
- Levelling rake: spreading sand and evening out bumps.
- Drag mat: working in sand and seed.
