Herb, perennial, dioecious, rhizomatous, glabrous except for tufts of hairs in the cataphyll and sheath axils. Rhizomes long, creeping or ascending, 5–7 mm diam.; cluster roots present. Culms to 2 m long, blue-grey, stout and erect toward the base, 4–7 mm diam.; upper branches slender and flexuose. Sheaths appressed, green to brown or straw-coloured, 0.5–3.0 cm long; lamina erect, herbaceous, filiform, 1–3 mm long. Male spikelets ellipsoidal, 3.3–7.0 mm long; glumes 4–13, acute to mucronate, keeled, 2.8–4.0 mm long, purplish to green or straw-coloured, glabrous or basally pubescent; mucro to 2.2 mm long. Female spikelets: 1-flowered, only the stigmas emerging from the subtending spathe; glumes 2 or 3, scarious, ovate, c. 0.3 mm long;. Male flowers: tepals 5 (or 6), lanceolate, acute; outer tepals slightly longer, 2.4–3.2 mm long; stamens 3, anthers exserted, filaments 3–5 mm long, anthers 1.2–2.0 mm long. Female flowers: tepals reduced to small membranous deltoid scales c. 0.7 mm long; ovary unilocular, style branches 3 (less often 2), fused 1/8–1/2 of length. Most female plants bear numerous large spikelet-like galls, 1.2–3.5 cm long with c. 80 sterile ‘glumes’, the ‘glumes’ 6–15 mm long, narrow-elliptic, acuminate, green or straw-coloured. Seed rarely produced and not seen. Culm anatomy: chlorenchyma of 1 layer of elongated peg cells interrupted by pillar cells over some outer vascular bundles, central cavity lobed or angular in the lower culm resulting from inner vascular bundles arranged in large aggregations that are separated by a broad band of sclerenchyma from the outer vascular bundles. Large spikelet-like galls with pale narrow-lanceolate scarious ‘glumes’ frequent on female plants.
Flood-beds or river banks, often in dense thickets in wooded or tall shrubland areas; in a region of high rainfall, in seasonally or permanently wet sands and peats; sites moist most of the year.
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