Annual wetland herb, 1.5–15.5 cm high. Leaves ± terete, erect or decumbent, c. 1–11 cm long, 0.2–0.8 mm diam.; basal sheath with fine acute auricles 0.4–1.8 mm long. Scape at fruiting erect or ascending, 1.2–10 cm long, 0.3–0.6 mm diam. Infructescence a raceme, 0.6–5.8 cm long, 6–14 mm diam.; pedicels 0.5–7.1 (–13) mm long. Fruits (2–) 4–59 per infructescence, semi-erect, narrowly pyramidal, usually slightly expanded at base into short points or spurs, 1.8–6.0 mm long, 0.5–0.8 mm diam. at greatest body width. Carpels 6, 3 fertile alternating with 3 sterile, united; mature fertile carpels readily falling, with dorsal surface ± flat or concave but with a low narrow longitudinal ridge down midline and narrow, sometimes finely winged, edges extended into short basal points or spurs, or ±basally rounded when spurs are near-absent; spurs 2 per carpel, directed laterally to somewhat downwards, sometimes upcurved when long, obtuse to acute, usually fully united by a thin translucent membrane, 0.1–0.45 (–1.6) mm long; central axis 3-winged, clearly visible.
Occurs in damp to wet, usually sandy soils (sometimes clay-loam), of mesophytic or ephemerally flooded freshwater sites, such as claypans, creek edges, swamps, roadside seepages, and shallow depressions, or sometimes edging salt lakes or in subsaline swamps. Also reported from granite, basalt, quartzite and limestone outcrops, coastal cliffs, and disturbed sites such as a sand mine, former farmland, grazed drained swamps, and a hilltop with copious rabbit droppings.
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