Korai (Manila grass)
Zoysia matrella
The most common lawn grass in Japanese gardens. It shrugs off hot, humid summers and establishes easily from sod. It goes dormant and brown in winter, then greens up again in spring.
At a glance
| Family | Poaceae |
|---|---|
| Season type | Warm-season |
| Heat tolerance | ●●●●● |
| Cold tolerance | ●●●●● |
| Shade tolerance | ●●●●● |
| Wear tolerance | ●●●●● |
| Drought tolerance | ●●●●● |
| Mowing height | 10–25 mm |
| Propagation | Sod / Plug |
| Upkeep | Medium upkeep |
| Native range | Japan, China, Southeast Asia |
Growing conditions
| USDA hardiness zones | 6–10 |
|---|---|
| Sunlight | Full sun |
| Watering | Medium |
| Growth rate | Slow |
| Soil pH | 5.5–7.5 |
| Common problems | Large patch / Thatch build-up / White grubs / Weed invasion |
How to grow it
Climate and sun
A warm-season grass that grows in summer and sleeps in winter. It suits lowland Japan and anywhere with hot, humid summers. Give it at least six hours of direct sun; below about four hours the shoots stretch, the turf thins, and it fades out over a few seasons. The top growth browns off in winter, but the roots are alive and green returns once soil temperatures pass about 15°C in late spring.
Planting
Lay sod — spring to early summer is the window. Butt the pieces together or leave 1–3 cm gaps; the gaps close within a season. Cultivate about 15 cm deep first, remove stones and perennial weed roots, and mix in coarse sand if drainage is poor. Top-dress lightly afterwards and roll or tread it down so roots meet soil.
Watering
Keep the surface damp for the first two or three weeks. After that rainfall is usually enough. Water in the morning when the blades turn blue-grey and footprints stay visible; evening watering leaves the leaves wet overnight and invites disease.
Mowing
Two or three cuts a month through the growing season, at 10–25 mm. Never take more than a third of the leaf at once — scalping down to bare stems costs a month of recovery.
Feeding
Nitrogen-led lawn fertiliser in late spring and midsummer, then a potassium-rich feed in early autumn. Skip feeding during heatwaves and dormancy.
Problems and winter
Large patch appears from the rainy season into early autumn; if rings of colour drop out, improve airflow and remove thatch. Rake out thatch in early spring once it exceeds about 1 cm. Winter browning is dormancy, not death — cut it short and leave it.