Imperata
Imperata cylindrica
Blades color red wherever the sun reaches them, and any all-green shoot is the invasive wild form reasserting itself.
- Type
- Grass · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Bronze, red and brown · Green
- Sunlight
- Full sun to partial shade; the color is best in full sun.
- Watering
- Keep it evenly moist, especially through the first season.
- Feeding
- Barely any feeding — a light compost mulch in spring covers it.
- Frost tolerant
- Yes
- Flowering
- July
- Pruning
- Cut to ground level in early spring — never in autumn.
- Overwintering
- Hardy to around -10°C, though the crown is worth protecting in cold sites.
- Apr–Jul Spring Growth
- Jul–Oct Flowering
- Oct–Nov Growing
- Nov–Dec Leaf Fall
- Jan–Apr Leaf Fall
- Plant spacing
- 15.7 in
- In-row spacing
- 15.7 in
- Between rows
- 19.7 in
- Square-foot density
- Not suited to SFG
- Root system
- Running rhizomes
- Working depth
- 4–12 in
- Can reach
- 18 in down where the soil allows
- Spread
- 2.5–5 ft across, about 2–4× the width of the plant
- Shallowest pot
- 12 in of soil
It travels underground, and it does not stop where you would like it to. Taking the tops off does nothing at all to the run, and every fragment left behind is a new plant. In open ground the only boundary that holds is a barrier sunk two spits deep, or a container with its rim standing clear of the soil.
The ornamental red form is well behaved, but the species behind it is cogongrass, one of the worst weeds in the world, spreading by sharp rhizomes that reseed and revert. Any green shoot appearing in a red clump is the wild form and comes out at once.
The habit is Imperata’s own; the figures are what that habit usually comes to at this size, not a measurement of this species. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
- All-green reverts — take them out at once, since the wild form is invasive.
- Too little sun and the red coloration fades.
- Not reliably hardy in cold, exposed sites — it may want winter protection.
Green-leaved grasses, like this one.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com