Slender perennial, in close-packed tufts from a shortly creeping rhizome. Culms 5-30 cm long, less than 0-5 mm in diameter, soft and usually flaccid; basal bracts light reddish brown. Leaves 1-3-(4) per culm, bright green, soft, usually flaccid, shorter than the culms; sheaths often tinged with redpurple. Inflorescence of 1-3 ovate spikelets, occasionally proliferous, subtending bract up to 6 times the length of spikelet. Spikelets 2-5-4 × 2-3 mm, varying in colour from pale green, through green tinged with red-purple to almost entirely black. Glumes (1)-1.2-1.8 mm long, ovate-elliptical, acute, keel green, prominent, often slightly excurrent, sides wholly cream, or with red-purple markings to almost entirely dark red-purple, but then often with pale cream nerves. Stamens occasionally 3 or usually 2 in lower glumes, usually only 1 stamen in upper glumes. Style branches 3. Hypogynous bristles 0. Nut 1—1.4 × 0-6—0-8 mm, obovate-elliptical, trigonous with angles slightly thickened, cream to sometimes light brown, minutely stipitate and apiculate.

Herba perennis gracilis, stolonifera. Culmi 5—30 cm longi, molles, plerumque flaccidi. Folia breviora culmis, viridia, mollia, plerumque flaccida; vagina saepe purpureo colore tincta. Spiculae 1—3, ovatae, nunc pallide virides, nunc purpureo tinctae, nunc paene nigrae; bractea subjacens inflorescentiam sexies longitudine superans. Glumae ovato-ellipticae, acutae, conspicua viridi carina. Stamina 3—2 in glumis inferioribus, in superioribus plerumque 1. Styli rami 3. Setae hypogynae 0. Nux trigona, angulis crassioribus, subalba vel interdum pallide brunnea.

Tufted perennial, often prostrate or drooping, from a slender ascending rhizome c. 0.5 mm in diameter. Culms 3-30 cm × 0-5-1 mm; 1-2 basal bracts per culm, membranous, grey-brown or sometimes red-purple. Leaves (l)-2-3-(4) per culm, shorter than or equalling culms; sheath often streaked with red-purple. Inflorescence c. (3)-4—5 mm high and (3)-5-9 mm broad, usually almost semicircular in outline, of 2—5 ovate, obtuse, closepacked spikelets, each usually dark red-purple, almost black below and green above to grey-brown later, rarerly entirely grey-green; subtending bract much exceeding inflorescence, up to 10 cm long, rigid, as wide as a foliage leaf, red-purple at base, sometimes a second shorter subtending bract is present. Glumes 2—2-5 mm long, lanceolate, acute, membranous, tinged with redpurple, keel very thick, green, slightly excurrent. Stamens 3 in lower glumes, to 2-1 above. Style branches 3. Hypogynous bristles 0. Nut about half the length of the glume, c. 1 × 0-5 mm, trigonous, with angles slightly thickened, elliptical, smooth, pale cream, shortly stipitate and apiculate.

Herba perennis spissis foliis, stolonifera. Culmi 3—30 cm long, subflaccidi. Folia breviora culmis vel eis aequantia; vagina saepe purpureo colore tincta. Spiculae 2—5, prope in formam semicirculi dispositae, compactae, rubro-purpureae basi, glaucae supra, vel rarissime glaucae per totam spiculam; bractea subjacens inflorescentiam longitudine multo superans, basi rubro-purpurea. Glumae lanceolatae, acutae, purpureo colore tinctae; Carina crassa, viridia. Stamina 3 in glumis inferioribus, in superioribus 2-1. Styli rami 3. Setae hypogynae 0. Nux c. dimidium glumae, trigona, laevis, pallida.