Tufted annual or possibly perennial. Culms erect, terete, striate, nodeless or 1-noded, 3–25(–55) cm high, 0.5–1.2 mm diam. Leaves with blade to 15 cm long; sheath straw-coloured to dark red-brown, striate, ± shining; mouth glabrous; ligule present. Inflorescence of 1 loosely hemispherical cluster of 6–16 spikelets, usually with 1–4 clusters below, erect, 1–15 cm long; lowest involucral bract to 17 cm long. Spikelets narrow-ovate, acute, 1–3-flowered, 2.5–7.5 mm long; glumes 4–6, lowest 2–4 empty, acute, red-brown to blackish, shining, with glabrous margins, midvein often scabrous; fertile glumes 2.0–5.5 mm long; hypogynous bristles 5 or 6, not plumose, shorter than or equalling nut. Nut trigonous, obovoid to subglobose, 3-ribbed, reticulate-pitted to trabeculate, glabrous, shining, whitish, 1.0–1.2 mm long, 0.6–0.8 mm diam. Flowers spring–summer.
LoM, MuM, Wim, GleP, Brid, VVP, VRiv, MuF, GipP, OtP, WaP, Gold, CVU, GGr, DunT, NIS, EGL, EGU, WPro, HSF, HNF, OtR, Strz, MonT, HFE, VAlp. Also SA, Qld, NSW, ACT, Tas. New Zealand, Japan. Mostly in seasonally damp or wet habitats, but reduced annual forms occur in some drier situations. A variable species, which may include more than one taxon.
