Rhizome with globose woody tubers. Stems to 90 cm high. Leaves broad. Inflorescence usually a compact head of 3-6 large spikelets with longer leaf-like bracts. Hypogynous bristles ½ length of nut. Stamens 3. Style-branches 2. Nut lenticular with concave sides.

Perennial, occasionally annual, tufted or rhizomatous, stout or slender herbs. Stems terete or 3-angled. Leaves flat or keeled with well-developed laminae, or filiform, reduced to basal sheaths. Inflorescence varying in number of spikelets and degree of branching, from a terminal, much-branched ± umbellate panicle with several leafy bracts, to an apparently lateral single spikelet or small cluster of spikelets, with subterete green bract appearing as a prolongation of the stem. Spikelets usually many-flowered. Glumes spirally imbricate round rhachilla, all floriferous or lower 1- (2) empty; flowers hermaphrodite. Hypogynous bristles c. 6, or often 0. Stamens 3 or fewer. Stigmas 3 or 2. Nut usually obovoid or ellipsoid, trigonous, plano-convex or biconvex. Cosmopolitan genus of c. 300 spp. Native spp. 20, adventive 6.

Infl. terminal or apparently lateral, corymbose, capitate, paniculate, spicate, or reduced to a single spikelet; subtending bracts several, lf-like, or 1 only, glume-like or culm-like, continuous with the culm. Spikelets 1-∞, us. many-fld. Glumes spirally imbricate round the rhachilla, all floriferous or the lowest 1, or rarely 2, empty; fls hermaphrodite. Hypog. bristles 2–8–(12), or 0. Stamens 3 or fewer. Styles 2- or 3-fid, not swollen at base. Nut us. obovoid, ellipsoid, trigonous, plano-convex or biconvex, us. apiculate. Glab., annual or perennial herbs, small and tufted, or slender and floating, or with a creeping rhizome and then often tall and stout. Culms terete or 3-angled. Lvs few to ∞ at base of culm, double-folded, terete or trigonous, or very slender and grasslike, or reduced to sheathing bracts. Cosmopolitan with c. 300 spp. Of the 23 N.Z. spp. only 6 are endemic; almost all the remaining spp. are recorded from Australia and many of these are cosmopolitan or widespread in the N. or S. Hemispheres.