Subaquatic perennial herb, rhizomatous; stems 1–2.5 m high, rooting at lower nodes, hollow, to 10–15 mm diam., glabrous below, hairy apically. Leaves with petioles 30–40 mm long, unwinged; lamina elliptic to lanceolate or ovate, 4–20 cm long, 1.5–8 cm wide, rounded to attenuate basally, entire to shallowly and irregularly toothed, acute, glabrous. Inflorescence dense, with hairy branches. Capitula many-flowered, hemispherical, (8–) 10–15 (–20) mm diam.; involucral bracts narrowly oblong to oblong-lanceolate, 4–5 mm long, obtuse to acute, glabrous or sparsely hairy basally. Corolla narrowly funnelform, ± saccate at base, white, covering top of achene. Achenes compressed, 5-angled, 0.5 mm long, papillose between ribs, glabrous.
Found in mud on the banks of dams, drains, freshwater lakes and creeks, or as an aquatic plant with floating stems growing in shallow water.
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