Annual wetland herb, 3–13 cm high. Leaves ± terete, often thread-like, 1–7 cm long, 0.2–0.5 mm diam.; basal sheath with broadly obtuse, rarely shortly pointed auricles to 0.25 mm long. Scape at fruiting erect to spreading, 2–13 cm long, 0.25–0.4 mm diam. Infructescence a lax open raceme, 1–6 cm long, 5–12 mm diam.; pedicels c. 1.5–5 (–9) mm long, 0.1–0.2 mm diam. Fruits c. 2–8 per infructescence, erect to somewhat spreading, narrowly trullate, (4–) 4.7–6.1 mm long, 1.1–1.6 mm diam. across the near-basal bulges. Carpels 6, 3 fertile alternating with 3 sterile, ventrally united; dorsal surface of mature fertile carpel with rounded edges and with a longitudinal groove containing a low narrow ridge down midline, each edge developing into a rounded bulge near carpel base or rarely bulges lacking; carpel tapered downwards below bulges; mature carpels readily separating; central axis 3-winged.
Chiefly a freshwater species recorded from a creek edge, from an Acacia woodland flat, and frequently from soils in ephemeral rock pools of granite outcrops; once from saline clay. Soils of red loam and of gritty red-brown clay recorded.
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