Cyperaceae Juss.

Annual or perennial herbs, rarely shrubs, or lianas, often with a grass-like or rush-like habit; the perennial species tufted or rhizomatous (often), sometimes stoloniferous, sometimes with tubers or bulbs; conical silica bodies present (in leaves); glabrous (usually) or with usually simple hairs on culms, leaves (usually on margins) or nutlets. Culms upright to ascending, rarely prostrate, triquetrous to terete, occasionally 4-or 5-angular, rarely compressed, usually solid, rarely hollow or septate. Leaves basal or near basal or 1 to several cauline, alternate, 3-ranked, rarely 2-ranked or multi-ranked; lower leaves (seldom all leaves) reduced to a sheath and rudimentary apical blade; leaf sheath closed (rarely open); ligule present (membranous or ciliate) or absent; contraligule present in Scleria; leaf blades (when present) simple, flat, folded, plicate, inrolled or terete, linear, occasionally pseudopetiolate, venation parallel, margins usually entire; stipules absent. Inflorescence aerial (or rarely amphicarpous, e.g. Bulbostylis striatella, Eleocharis caespitosissima, Trianoptiles solitaria), simple or compound, variously umbel-like (sometimes referred to as anthelate), panicle-like or head-like, or reduced to a single inflorescence unit; inflorescence units either indeterminate (= spikelets) or sometimes determinate (= pseudospikelets/spicoids); bract(s) subtending the inflorescence 1 or more (often called involucral bracts or, when 1, sometimes called a primary bract), the lowest one(s) often much exceeding the inflorescence and resembling the leaves or sometimes resembling the culm, the others gradually smaller, the upper ones (and sometimes all) small and glume-like. Spikelets or pseudospikelets either solitary or clustered, terete or compressed, 1-to many-flowered, terminal and/or lateral, spirally arranged or sometimes distichous (e.g. Blysmus, not in Australia); spikelets each subtended by a bract (sometimes called a spikelet bract), and often bearing a small modified bract called a prophyll at the base. Flowers bisexual or rarely unisexual and the species then monoecious or rarely dioecious (some Carex  and Cyperus species not occurring in Australia, some Scleria species), actinomorphic, inconspicuous, each usually solitary within a bract here called a glume, arranged along a rachilla (spikelet axis); rachilla persistent or caducous, straight or flexuose, sometimes winged; glumes arranged either distichously or spirally on the rachilla or the proximal glumes arranged spirally and the distal ones arranged distichously or vice versa, caducous or persistent, one or more of the lower or upper ones often empty. Perianth often absent or reduced to (1–) 3–6 (–30) hypogynous scales, bristles or hairs, very rarely subtepaloid or disc-like, persistent. Stamens (1–) 3 (–6 or seldom more), filaments usually free, sometimes long persistent and attached to base of nut (some Gahnia, some Machaerina); anthers basifixed, tetrasporangiate, dithecal, dehiscing by longitudinal lateral slits, anthers often with an apical appendage and sometimes also basal appendages; pollen grains borne in pseudomonads. Gynoecium of (2–) 3 (–4) connate carpels. Ovary superior, placentation basal, 1-locular; style apical, ± deeply divided into 2 or 3 (rarely 4) branches, rarely simple; style filiform or base sometimes enlarged and may persist in fruit; stigmas 2 or 3 (–4). Ovule 1. Nectaries absent. Fruit rarely drupaceous (Scirpodendron), usually a 1-seeded nutlet, trigonous, triquetrous or biconvex; pericarp usually hard (rarely fragile as in Scleria); gynophore sometimes present (e.g. Ficinia, Mapania). Embryo embedded in copious mealy endosperm.

Occupying diverse habitats, with a preference for open and aquatic habitats, but Australia, like South Africa, is also home to a large diversity of dryland species.

Notwithstanding the diversity within Cyperaceae, the family is of limited economic importance in the commonly accepted sense. Very few species are cultivated as crops. The most important of these is Eleocharis dulcis which provides the commercial Chinese Water-chestnut. Cyperus cyperoides, C. esculentus (commonly known as Chufa Sedge, Yellow Nutgrass and by other names, and grown mainly in Africa) and C. rotundus (Nut Grass) also have edible subterranean storage organs (Reznicek 1998, Judd et al. 2016). Simpson and Inglis (2001) gathered information on the economic and ethnobotanical importance of Cyperaceae, showing that about 10% of the family are used at local and regional levels in the tropics. In some northern hemisphere countries, Carex species are important as pasture, and may be managed as in Carex lyngbyei (Lyngbye's Sedge) in Iceland (Reznicek 1998). Cyperaceae species are traditionally used in weaving (e.g. baskets, mats), to build rafts and houses, and for thatching and paper-making. Cyperus papyrus (Papyrus, Paper Reed, Nile Grass), native to Africa, was used by the ancient Egyptians to make a form of paper. The species is still of local importance in Africa as a source of fuel (Reznicek 1998). Some Cyperaceae taxa have medicinal uses, e.g. Cyperus rotundus (Sivapalan 2013, Kamala et al. 2018), Cyperus articulatus (Bum et al. 1996), and potentially several Lepidosperma species (Barrett 2013; Duke et al. 2017; and references therein). Cyperaceae are generally not very well represented in horticulture, although a few species are grown as semiaquatic plants by pools and lakes or in hanging baskets (HortFlora). A growing number of non-Australian Carex species are cultivated for ornament, including the New Zealand species Carex albula, Carex buchananii, Carex comans, Carex flagellifera, Carex petriei, Carex secta, Carex testacea and Carex virgata, all of which readily self-seed in gardens, and are likely to become naturalised and invasive. Other species sold include Carex morrowii (from Japan) and Carex riparia (north Africa, Asia, Europe). Several Cyperus species are also commonly cultivated in gardens and parks, including Cyperus papyrus, Cyperus prolifer and Cyperus involucratus. A number of large, fast-growing wetland sedges, including Baumea articulata, Bolboschoenus species, Carex fascicularis, Cladium procerum, Eleocharis sphacelata and Schoenoplectus tabernaemontani are used in environmental remediation (e.g. stabilising substrates), the construction of wetlands and water and sewage treatment (filtering water) because of their capacity to absorb excess nutrients.