Perennial; stems to 3 m long, floating, stoloniferous. Petioles of basal leaves 8–42 cm long; blades broad-ovate to c. circular, crenate to crenate-dentate, deeply cordate, 3–13(–15) cm long; blades of stem leaves smaller, sometimes reniform to c. deltoid. Flowers heterostylous, 8–14 in a cluster subtended by 1–4 stem leaves or rarely in spaced pairs along a short inflorescence; calyx 5.5–10(–16) mm long; corolla 20–40(–50) mm diam., lobes (4–)5(–6), with broad laciniate wings and keel; stigmas mostly (2–)5, each with a vertical papillate wing decurrent on the style, the decurrent portions forming persistent stylar ridges. Capsule (4–)6–9 mm long, usually much shorter than calyx; seeds ellipsoid, strongly laterally compressed, (0.5–)0.6–0.9 mm long, pale brown, usually smooth, sometimes granular around edges; caruncle absent; minute hard projection present beside attachment point. Flowers mostly Sep.–May, fruits Nov.–Mar.