A perennial sedge with a network of underground tubers, regarded as one of the world's most troublesome agricultural weeds.
Nut grass or purple nutsedge (Cyperus rotundus, family Cyperaceae) is a perennial, grass-like sedge with tufts of stems 10 to 50 cm tall, occasionally 75 cm. It spreads fast underground by slender rhizomes, each ending in a tuber from which a new tuft grows. Its tubers are a popular herbal medicine, listed in the pharmacopoeias of several countries, and they are gathered from the wild mainly for medicine but also for food, essential oil and basketry; it is sometimes grown for its edible tubers. It is classed as Least Concern on the IUCN Red List (2018).
It is widespread from the warm temperate zone to the tropics of southern Europe, Africa, Asia, Australia, the Pacific and the Americas, on roadsides, sandy fields and farmland, and in many wet places such as seasonally wet grassland, swamps, ditches, the edges of ponds and lakes, and riverbanks. It grows best at 24 to 32°C, prefers moist sandy loam in sun, and is killed only by frosts of -5°C or lower. It is one of the world's most damaging weeds of farmland, hard to eradicate because it spreads by seed as well as by its roots, and it is subject to legal control in several countries. In East Africa it has become a particularly serious weed in irrigation schemes and in coffee.
Source: Useful Tropical Plants database (Fern, K.).
Tubers are used across Africa and Asia for digestive complaints and fever and as a diuretic and emmenagogue, and are widely studied for anti-inflammatory and antimicrobial activity.
Spreads aggressively through underground tubers and rhizomes; a persistent weed of cultivated land, not deliberately grown.