Monoclinous, emergent. Stems short, erect, terete, rhizomatous. Leaves basal, submersed or emersed, erect, long-petiolate; petiole aerenchymatous; blade linear to narrow-lanceolate, apex acute, base attenuate. Inflorescence few-flowered, obscurely paniculate, umbel-like. Flowers longpedicellate, sepals short, recurved, persistent; petals much longer than sepals, orbicular, white to pink; stamens 6 in pairs opposite petals; carpels many, free; achenes forming an echinate head, achenes oblong, elliptic, with 5 costae. 2n = 14, 16, 18, 22.