Plants perennial, rooted in mud. Vegetative stems contracted, rhizomatous. Flowering stems erect, to 120 cm. Sessile leaves: blade linear. Petiolate leaves emersed; stipule 7–29 cm; petiole distinctly constricted just below blade, to 60 cm; blade lanceolate to cordate, 6–22 × 0.7–12 cm. Spikes with up to several hundred flowers, 2–15 cm; spathes 5–17 cm. Perianth mauve, tube 3–9 mm, limb lobes oblanceolate, 5–8 mm, distal central lobe with 2-lobed yellow spot; proximal stamens 7–13 mm, distal 1.5–6.3 mm; style 3-lobed. Utricles with dentate ridges, 4–6 × 2–3 mm.