Cyperaceae

Non-woody grass-like plants with stems that are usually triangular in cross section; leaves three-ranked with a closed sheath, parallel veins and cone-shaped silica bodies (these bodies do not occur in other families of plants with parallel veins); sepals and petals absent or replaced by bristles, hairs or rarely scales; and fruit a hard-shelled achene (nutlet). Includes Sedges, Beakrushes, Bulrushes, Clubrushes, Cottongrasses, Flatsedges, Spikerushes, and Twig-rush. Identification usually requires mature fruit.

Flowers are arranged in one or more spikelets that have a central stalk bearing an overlapping spiral or two-rowed series of scale-like bractlets, each of which supports a tiny flower in its axil. Spikelets may be arranged in racemes, spikes, heads, panicles or umbels. Sepals and petals absent, or modified into 1 to many (often 6) bristles that may be short and flattened or long and hair-like, may be barbed or hairy in some Beakrushes, and often persist in fruit. Plants may produce pollen and fruit on the same flower, on separate flowers on the same plant, or on separate plants. Stamens mostly 1-3, separate, protruding from the spikelet when pollen is being released. Carpels 2 or 3, fused; ovary situated above the point of attachment of other flower parts (if present), with one chamber, surrounded by a hollow vase-shaped structure (called a perigynium) in Carex; styles 2 or 3, often long. Fruit a solitary hardened achene, that is triangular (in species with 3 styles) or lens-shaped (in species with 2 styles). Tip of achene in Spikerushes often has a small knobby projection (tubercle).

Leaves alternate or basal, in 3 vertical rows on stem, and with a tube-shaped sheath that has fused margins along the side of the stem opposite the leaf blade (if present). Leaf blades flat, V-shaped, triangular, cylindrical, inrolled and wiry, or absent, linear, unlobed and with smooth margins or sometimes with tiny teeth. Stipules absent, ligule often absent.

Stems usually triangular in cross section (may be round, flattened or several angled in Spikerushes and some Bulrushes), filled to the centre with pithy tissue, nodes inconspicuous and not swollen. Plants of this family generally have rhizomes and are especially well represented in wetlands in temperate and colder regions.