Imperata cylindrica aka Sharp Grass

Imperata cylindrica, or cogongrass, is a perennial in the grass family. Its native range runs from the Mediterranean through Africa to Afghanistan. It now grows as a weed across many warm regions. It forms upright clumps and spreads fast through underground rhizomes. These stems help it survive drought and regrow after fire.

Size reports differ between sources and growing regions. Garden profiles give heights from 1.6–4 feet [0.5–1.2 metres]. Reported clump widths reach 4 feet [1.2 metres]. In Florida, leaves can reach 6 feet [1.8 metres]. The RHS describes the foliage as deciduous. Stiff, flat blades range from yellow-green to green. Each blade has a pale midrib set off centre. The pointed leaves have fine teeth along their edges. Sharp silica crystals make these edges harsh to touch. White, branched rhizomes can reach 4 feet [1.2 metres] deep.

The flowers form narrow, silvery panicles above the leaves. Northern plants flower less often than plants in tropical areas. The RHS lists summer bloom, while Florida plants flower in spring. Disturbance, such as mowing, can also trigger bloom there. Wind carries pollen between flowers. White, fluffy seed heads follow the blooms. Silky hairs help the seeds travel on the wind. Animals and equipment can also move seeds to new sites.

The plant grows in sun or some shade. It favours moist soil that drains well and contains humus. It accepts clay, loam, sand, and a broad pH range. Established plants can withstand drought and poor soil. NC State lists USDA zones 5–9; the RHS gives H4. The RHS advises winter mulch where the climate is cold. It also lists borders and pots as garden uses. Yet this species is invasive and hard to control. It can crowd out other plants and raise wildfire risk. Serious pests and diseases seldom trouble it.

People have used this grass for erosion control and ground cover. Leaves provide fibre for paper, mats, bags, and raincoats. Stems supply roof thatch, while flower heads fill pillows. Young shoots and flower heads have been eaten cooked. The fibrous roots contain sugar and starch and are chewed. Plant ash has served as a salt substitute. Roots and flowers also have traditional medicinal uses. PFAF reports no known hazards, but the sharp leaf edges remain a physical risk.