Perennial ryegrass
Lolium perenne
The fastest grass to green up from seed, and tough under foot — hence its use on school grounds and sports fields. It struggles in Japanese summers, so it is also sown over warm-season turf for winter colour.
At a glance
| Family | Poaceae |
|---|---|
| Season type | Cool-season |
| Heat tolerance | ●●●●● |
| Cold tolerance | ●●●●● |
| Shade tolerance | ●●●●● |
| Wear tolerance | ●●●●● |
| Drought tolerance | ●●●●● |
| Mowing height | 20–50 mm |
| Propagation | Seed |
| Upkeep | Medium upkeep |
| Native range | Europe, West Asia, North Africa |
Growing conditions
| USDA hardiness zones | 3–7 |
|---|---|
| Sunlight | Full sun |
| Watering | High |
| Growth rate | Fast |
| Soil pH | 5.5–7.5 |
| Common problems | Rust / Brown patch / Dollar spot / Snow mould / Pythium blight |
How to grow it
Climate and sun
A cool-season grass that grows in spring and autumn. It works year-round in cold regions but is best treated as temporary where summers are hot and humid. Its most common use in Japan is winter overseeding — sown over dormant warm-season turf to keep colour through the cold months. It prefers full sun and is not especially shade tolerant.
Planting
Sow seed. Germination in three to seven days is its great strength, which also makes it the go-to for patching. For overseeding, sow from late September to mid-October once soil temperatures drop below about 25°C. Mow low and rake out thatch first so the seed reaches soil.
Watering
It has little drought tolerance. Water once or twice a day until germination, and keep at least two deep morning waterings a week through summer after that.
Mowing
Fast growth means weekly cuts or more in spring and autumn, at 25–50 mm. Letting it get long traps humidity at the base and brings disease.
Feeding
For autumn sowings, feed lightly in late autumn and again in late winter. Too much nitrogen softens the leaf and invites rust.
Problems and winter
Rust, brown patch and snow mould are the usual troubles — yellow dust on your shoes after mowing means rust. In hot-summer regions it dies out from early summer, so plan the handover to the warm-season grass underneath rather than fighting for it.