Perennial, dioecious herbs. Rhizomes creeping or tufted, woolly. Stems erect, flattened, green tissue interrupted by lines of enlarged epidermal cells or by pillar cells (lacking chloroplasts), glabrous or hairy, unbranched. Leaves reduced to sheathing bracts, 10–25 mm long. Male and female inflorescences similar, ovoid, oblong-ovoid or globular, made up of several clusters of spikelets. Spikelets in distal axis of leaves, shortly pedicellate, several- to many-flowered, (males with many more than females), subtended by 2–many glume-like floral bracts. Flowers with 4 membranous (glume-like) perianth parts. Female flowers with 2 staminodes; ovary bilocular; style with 2 branches. Fruit a septicidal capsule.
