Sowing a new lawn from seed

When to sow

Early autumn is the best window for cool-season grass: the soil is still warm from summer, autumn rain helps, and weeds are slowing down. Spring is the second choice; the grass comes up well but has less time to root before summer dry spells. Avoid peak summer heat and hard frost.

How much seed

For a park or sports mix of ryegrass, bluegrass and fescue, sow 25–35 g/m², about 5–7 lb per 1,000 sq ft. More seed does not make a thicker lawn; crowded seedlings compete and thin out. Weigh the seed for the whole area before you start so you know you used the right amount.

How to sow

1. Split the seed into two equal halves.
2. Spread the first half walking lengthwise, the second walking crosswise. A spreader gives a far more even result than sowing by hand.
3. Rake lightly so the seed sits 0.5–1 cm (about ¼–½ in) deep. Seed left on the surface dries out or feeds birds; seed buried deeper struggles to come up.
4. Roll or tread the area so every seed is in firm contact with the soil.

What decides whether it works

Water. New seed must stay constantly moist for three to four weeks, which usually means a light watering once or twice a day. If you are not on site every day, set up a sprinkler on a timer before you sow. Do not use a weed pre-emergent anywhere you have just sown: it stops grass seed germinating too.

The steps before this one matter as much: a soil pH test, a level bed and a starter fertilizer high in phosphorus. The first cut comes once the grass reaches 8–10 cm; see first mow of a new lawn.