Description from Flora of China
Arundo australis Cavanilles, Anales Hist. Nat. 1: 100. 1799; A. phragmites Linnaeus; Phragmites communis Trinius.
Robust perennial from an extensive creeping rhizome; overground stolons sometimes present, straight, nodes glabrous. Culms up to 2 m or more tall, ca. 6 mm in diam., usually farinose below nodes, nodes glabrous or pubescent. Leaf sheaths light green, glabrous or thinly hairy; leaf blades usually drooping, up to 50 × 1–3 cm, smooth or margins scabrous, tapering to a filiform apex; ligule a minute membranous rim, ciliate, hairs 0.2–0.6 mm. Panicle 20–50 × ca. 10 cm, branches of lowermost whorl usually spiculate to base, densely hirsute at insertion; pedicels 2–4 mm, glabrous or pilose only at base. Spikelets 10–18 mm, florets 2–5; glumes acute, lower glume up to 1/2 length of lowest lemma, 3–5 mm, upper glume 6–9 mm; lowest lemma linear-lanceolate, 8–15 mm; floret callus with hairs equal to lemma; bisexual lemmas very narrowly lanceolate, 9–16 mm, apex long attenuate. Fl. and fr. Jul–Nov. 2n = 36, 44, 46, 48, 49, 50, 51, 52, 54, 84, 96, 120.
This is an extremely polymorphic, cosmopolitan reed with numerous chromosomal variants and ecotypes. Plants from the high Himalayas sometimes form short, leafy tufts with strongly distichous, short, pungent leaf blades. Similar variants occur elsewhere in the world in extreme conditions.
Moist places along river banks and lake margins, forming large colonies. Throughout China [cosmopolitan].