A patchy lawn in spring is tempting to fix straight away. In Australia, whether and when to sow depends almost entirely on what kind of grass you have, and for the most popular backyard lawn, soft leaf buffalo, the answer is not seed at all.
When should you sow warm-season lawn seed?
Couch, kikuyu and zoysia seed needs warm soil, above about 18°C and staying there. That means:
| Region | Best window |
|---|---|
| Sydney, Brisbane, Perth | Mid-October to December, or February to early March |
| Adelaide | October to November |
| Melbourne, Canberra | November to December |
Summer sowing works if you can keep the seed moist, which is the hard part under water restrictions. Autumn sowing of warm-season seed often fails, because the young grass has too little time to establish before it goes dormant.
When should you sow cool-season seed?
Tall fescue, ryegrass and fine fescue lawns are common in Melbourne, Canberra, Hobart and the southern tablelands. For those, autumn is best: March to April, when the soil is still warm but the air has cooled. Spring works as a second choice from September to October.
Oversowing a couch lawn with perennial ryegrass in autumn is a common trick to keep it green through winter. The ryegrass fades out as the couch takes over in late spring.
Why can’t you sow buffalo?
The soft leaf buffalo varieties sold in Australia, like Sir Walter, Palmetto and Sapphire, are grown and sold as turf. Thin buffalo repairs itself with runners once it is growing strongly in late spring, or you can plug bare patches with turf cut from the edge of the lawn.
How do you pick the right day?
Soil warmth and the forecast. Here is the buffalo lawn in Sydney on a cool September evening:
The app scores it 33, wrong season. For warm-season grass, the prime sowing window is late spring into early summer, not the middle of September, and no rain is forecast to keep seed moist. The app estimates soil temperature from air temperature and month, and on a 12°C evening that comes out at around 9°C. The card calls that good, which is true for ryegrass or fescue seed, but for couch and kikuyu it is far too cold, and the wrong-season verdict is the one that counts. By late October the same lawn in Sydney will look very different.
The app shifts its calendar by six months for the southern hemisphere, so September is treated as early spring, not early autumn.
How do you sow into an existing lawn?
The steps are further down the page. The one that matters most is soil contact. Seed sitting on thatch germinates and dies. For couch and kikuyu, scalping or scarifying first gives the seed bare soil to land on; see When to Scarify Your Lawn. Then keep the surface moist every day until the grass is up, within your local water restrictions.
What a Green Lawn checks soil warmth and rain for your address every day and scores sowing, fertilising and scarifying for your grass type.