Perennial, aquatic herb from slender rhizomes; stems annual, usually unbranched, 5-40 cm long, about 2 mm wide.
Tufted at the rhizome nodes, flat, 5- (7-) veined, the margins toothed towards the tips, (30) 50-150 cm long, 2-4 mm wide.
Inflorescence of 5- to 40-cm long, stalked spikes of male and female flowers on different plants; female spikes usually 1 per stem, 1-sided, 4 (5) cm long, with 5-12 flowers; male spikes 5-6 cm long.
Nutlets, 3-4 mm long, the base with 2 downward projecting, hornlike lobes.
Until the work of Phillips (1970), material of this species was included in P. scouleri.
If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.
Illustration Source: The Illustrated Flora of British Columbia