E-Flora BC: Electronic Atlas of the Flora of British Columbia

General:
Perennial, aquatic herb from weak rhizomes; stems floating, 20-60 cm tall.

Leaves:
Alternate, limp, unkeeled, flat, floating, linear with sheathing bases, 40-60 cm long, 2-8 mm wide.

Flowers:
Inflorescence simple, of 1 to 3 female heads below and 1 male head above, the heads globe-shaped, the female heads 0.5-1.2 cm wide, axillary, sometimes borne above the leaf axils, usually unstalked or sometimes stalked below; perianth segments 6, attached near the top of the flower stalk; stigma 1; anthers less than 0.8 mm long.

Fruits:
Achenes, 2-4 mm long, barely or not constricted at the middle, beaked, the beaks 0.5-1.5 mm long, curved; seeds 1.