Phragmites australis (Cav.) Trin. ex Steud.

Robust perennials 1.5–3 m, with wide flat leaves borne along stout reed-like stems and with stout creeping rhizomes to 2 cm diam. Leaf-sheath rounded, chartaceous, glabrous, with numerous, minute cross-veinlets. Ligule c. 1 mm, truncate, short membranous, long ciliate. Collar brownish on both surfaces with dense, appressed, minute hairs, and ephemeral hairs to 6 mm on margin. Leaf-blade 40–60 × 1–3 cm, coriaceous, linear, somewhat narrowed at base, much-tapered above, smooth, but abaxially scabrid towards long, filiform, scabrid tip, margins scabrid above; disarticulating at ligule. Culm erect, rigid, usually simple, internodes glabrous. Panicle 20–30 cm, erect or finally drooping, purplish to brownish; branches numerous, glabrous except tufts of long (4 mm), silky hairs at nodes. Spikelets 10–14 mm, 3–6-flowered, finally widely gaping, lowest floret ♂ or Ø, others ☿. Glumes unequal, persistent, 3–5-nerved, chartaceous, glabrous, ovate-lanceolate, acute; lower c. 4 mm, upper c. 6 mm. Lemma of basal floret 9–10 mm, 3-nerved, narrow-lanceolate, membranous, acute, persistent; lemmas of perfect florets shorter, narrower, tip long-acuminate to caudate. Palea 3–4 mm, « lemma, keels ciliate. Callus 0.5–1 mm, with dense long (6–8 mm) silky hairs. Rachilla c. 0.2 mm, glabrous, prolongation 0.5 mm, glabrous. Lodicules 0.3 mm, obovate, nerved, glabrous. Anthers 1.5–2 mm. Gynoecium: ovary 0.5 mm; stigma-styles 2 mm. Caryopsis not seen.

[From: Edgar and Connor (2000) Flora of New Zealand. Volume 5 (second printing).]