2n = c. 44–45

Perennial herbs, tufted, rhizomatous or stoloniferous. Stems usually 3-angled and solid, rarely terete and hollow. Leaves tristichous, usually linear, mostly crowded at base of stem and sheathing, sheath closed, with a minute, membranous ligule. Plants usually monoecious, rarely dioecious. Inflorescence a spike, cluster of spikes, or panicle; bracts leaf-like or setaceous. Spikes sessile or pedunculate, unisexual or bisexual, composed of numerous 1-flowered spikelets, each subtended by a glume. Flowers unisexual, perianth 0. Male flower with 3 stamens (rarely 2). Female flower a single pistil enclosed in an utricle; style 1, branched above to 2 or 3 stigmas projecting from utricle. Nut trigonous or biconvex, enclosed within persistent utricle. A genus of 1500-2000 spp. in cold and temperate regions or at high altitudes in the tropics. Native spp. 73, adventive 22.

Plants us. monoec., rarely dioec. Infl. a panicle, compound raceme, compound spike, cluster of spikes, or a single spike; bracts subtending panicles, spikes or individual spikes of compound infls, us. lf-like, sheathing or not sheathing. Spikes sessile or pedunculate, unisexual or bisexual, composed of ∞ 1-fld spikelets; each spikelet subtended by a glume. Fls unisexual; perianth 0. Male fl. with 3 stamens (rarely 2). Female fl. a single pistil enclosed in a sac-like organ (utricle); style 1, branched above to 2 or 3 stigmas which project from the small orifice at the apex of the utricle. Nut trigonous or biconvex, enclosed within the persistent utricle. Perennial herbs, either tufted, or with creeping subterranean rhizomes. Culms us. trigonous and solid, rarely terete and hollow. Lvs tristichous, us. linear, mostly crowded at base of culm and ensheathing it, with a very minute, membr. ligule at the junction of lf and sheath. A genus of c. 1,500–2,000 spp. in cold and temperate regions or at high altitudes in the tropics. Of the 73 N.Z. spp. 61 are endemic.

Infl. a simple terminal spike with unisexual fls, ♂ at top, ♀ lower, in 1-fld spikelets each subtended by a glume; ♂ with 3 stamens; ♀ surrounded by a plano-convex to trigonous, us. glab., occ. hispid, closed sac or utricle; style-branches 3, protruding from mouth of utricle; nut trigonous; axis of spikelet, the rhachilla, produced beyond mouth of utricle and terminating in a rigid glume which is sharply reflexed to form a hook. Perennial herbs, tufted or shortly rhizomatous. Culms ± trigonous, occ. terete, with bract-like sheaths at base. Lvs grass-like, linear, us. Shallowly channelled, almost flat towards the base, flanged-channelled towards the tip, occ. involute, rarely plano-convex, margins ± scabrid, tip us. trigonous, lf-base sheathing. Between 40 and 50 spp., mainly in the S. Hemisphere but not found in S. Africa. Most N.Z. spp. are endemic but 2 are recorded from elsewhere in the Pacific.