Rhizome purple, thick, creeping. Leaves narrowly linear, 7-nerved, denticulate upwards. Male flowers long peduncled, larger than the leaves. Carpels half-ovoid, slightly keeled, entire or indistinctly repand.
Stems with annular scars at the nodes left by fallen leaves. Leaves up to 40 cm x 4 mm, rounded-obtuse, 7- to 9-veined, spinulose-dentate towards the apex. Peduncles of male flowers 7-10 cm; anthers 11-15 mm. Fruitlets 8 mm (excluding the short beak), laterally compressed, semicircular.