Perennial aquatic or marsh herb, robust; stems 30–40 cm tall, mostly 5–6 mm diam., papillose, rooting at nodes in fully emergent plants. Leaves dimorphic; submerged leaves in whorls of 4–6, broadly ovate to orbicular, mostly 15–45 mm long, pectinate, with 17–23 pinnae; emergent leaves in whorls of 4–6, linear, mostly 15–45 mm long, sometimes papillose at base, margins with 12–18 teeth on distal three-quarters. Bracteoles of male flowers oblong, 0.6–0.8 mm long, fimbriate; bracteoles of female flowers minute; flowers solitary or in fascicles of 2 or 3. Male flowers sessile; sepals 4, lanceolate, c. 0.6 mm long; petals 4, 2.5–3.6 mm long, white-hyaline, caducous; stamens 8. Female flowers shortly pedicellate; sepals and petals absent; ovary 4-celled, styles more or less sessile, stigmas reddish-purple. Fruit cubiform, green to reddish-purple; mericarps narrowly ovoid, 0.8–1.0 mm long, apex oblique, dorsal surface coarsely papillose. Flowers Sep.–Apr.
MuM, Wim, VVP, VRiv, MSB, RobP, MuF, Gold, CVU, DunT, NIS, VAlp. Also SA, Qld, NSW. Found mainly along the Murray River and its tributaries where it grows in shallow water or on mud.
Readily distinguished from its closest relatives by its robust habit, irregular gold-coloured papillae on the stems, flowers and fruit in fascicles and mauve to purplish stigmas.
