Description

Herb 50-150 cm high, from a rhizome; stems 4-angled. Stipular sheaths 10-20 mm, convolute, early deciduous. Leaves 30-90 × 8-15 mm, linear-lanceolate, sessile, all submerged, shining, translucent; apex obtuse, apiculate; margin finely serrate, markedly undulate when mature. Spikes 5-10-flowered, somewhat lax. Drupe 2-4 mm, ovoid-acuminate, laterally flattened; beak nearly as long as fruit, falcate, tapered.