Cyperus cyperoides aka Pacific Island Flat Sedge

Cyperus cyperoides is a sedge in the family Cyperaceae. Its home range spans Africa to the Pacific. This includes tropical Asia and Australia. It also grows in warm-temperate parts of this broad range. Plants brought elsewhere have spread in parts of the Americas and Pacific. Kew links this species to a wet tropical climate. It is not native to Britain or Ireland.

The plant grows in loose tufts that look like grass. Its stems, called culms, reach 0.3–2.5 feet [0.1–0.75 metres]. One source gives a height of about 1.6 feet [0.5 metres]. Sources differ on its life span: one year or more. Kew calls it perennial, or a rhizomatous geophyte. These terms mean it lives for years or has stems below ground. Other sources describe short, hard rhizomes beneath the stems. Rhizomes are stems that grow below ground, not roots. The supplied species accounts give no clear season for flowers.

In the wild, it grows in sun or light shade. It grows in grassland, by roads, and along ditch edges. It also grows by rivers and in other wet spots. It lives in forest gaps, regrowth, and thickets too. Most records come from below 5,906 feet [1,800 metres]. Some reach about 10,499 feet [3,200 metres]. Its wide range of sites backs its reputation for adapting well. The evidence gives no frost limit or garden hardiness zone.

People grow this sedge for its looks and harvest wild plants. In parts of Africa, they also grow it for food. People roast the rhizomes, mainly when better foods are scarce. This does not mean that all parts are safe to eat. People also use the roots to make brushes. Useful Tropical Plants reports no known hazards for this species. This does not prove it is safe for pets or every use.

Folk uses include cures for worms, coughs, and fever. Reports also list uses for skin problems, wounds, and toothache. These folk uses do not prove that the treatments work. The plant can become a weed in gardens. Reports list it as invasive in Hawaii and Fiji. Weigh its use for looks against the local weed risk. Useful Tropical Plants cites a 2013 Least Concern assessment. That account says the plant is widespread, with no major known threats.