Ecdeiocolea rigens B.G.Briggs

Herb, monoecious, perennial, extensively rhizomatous forming widely-spaced clumps or lines of culms or spread diffusely over areas up to 2 m across. Rhizomes 4–6 mm diam., with tufts of long (3–6 mm) hairs covered by glabrous overlapping dull brown scales. Cataphylls oblong, lower ones c. 1 cm long, upper ones to 22 cm long, 5–10 mm wide, scarious, dull brown, paler toward the apex; tapering to a rounded apex, lower cataphylls appressed, upper ones erect or recurved and mostly weathering and frayed distally. Culms unbranched, of a single internode, rigid when fresh, crowded or 5–20 mm apart on the rhizome; glabrous, striate, pruinose toward the base; with a persistent scarious sheath to 2–3 cm long at the base of the peduncle which is continuous with the culm but more slender; culms (including peduncles) to 1.8 m high, 2–3 mm diam. near the base. Spikes solitary, terminal, cylindrical to ovoid, compact, with 30–45 glumes and flowers (fewer or wholly aborted in drought seasons); 20–45 mm long, 7–12 mm wide, with zones of female and male flowers alternating once or twice along the spike axis, the basal zone mostly female; flowers spirally arranged in 5 ranks, on very short pedicels. Glumes ovate-cuneate, rigid, brown, not glossy, 5–7 mm long, glabrous but towards the apex densely ciliate with short pale hairs. Tepals 6, 2 outer lateral tepals keeled. Male flowers with 6 scarious, brown, rigid, narrow-ovoid tepals 4–6 mm long, glabrous except for a fringe of very short hairs distally and on some tepal keels; outer lateral tepals keeled; stamens 4. Female flowers with tepals similar to the males but ovoid, 5–6 mm long; ovary initially 2-locular and styles 2, but only 1 carpel developing. Fruit a small globose nut (structurally an achene), pale brown with dark blotches, with a rugose band on one side at the position of the carpel margins, rugose and darker toward the apex, 3–4 mm long, shed with attached tepals, a short stout stipe c. 1 mm long and the style base forming a short conical beak. Seeds with an irregular pattern of longitudinal lines of convex cells. Culm striate with narrow grooves extending to the base of the chlorenchyma; stomates on sides or near base of grooves; ridges without a central sclerenchyma rib.

Sandplains of yellow sand and in shrubland in a region of low rainfall. It is commonly found growing with the more widespread Ecdeiocolea monostachya.