General:
Perennial aquatic herb from strong rhizomes; stems up to 150 cm long, branched.

Leaves:
All submersed, triangular-lanceolate, thin, flat, dark green, 3-10 cm long, 1-3 cm wide, the tips blunt, clasping the stem, the stipules 1-3 cm long, coarse, disintegrating into persistent whitish fibres that remain even on old plants, fibrous or stringy; floating leaves absent.

Flowers:
Inflorescence spikelike, the spikes 1-4 cm long, with 6 to 12 whorls of flowers, the stalks inflated, club-shaped, 1.5-25 cm long.

Fruits:
Achenes, widely egg-shaped or almost rounded, 2.5-3 mm long, 2.3-2.7 mm wide, the beaks prominent, triangular, the keels absent.

Notes:
Stem anatomical characters interlacunar bundles and subepidermal bundles absent, pseudohypodermis 1 cell thick, endodermis of O-cells.

Source:  The Illustrated Flora of British Columbia

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

Synonyms and Alternate Names:
Potamogeton perfoliatus subsp. richardsonii (Benn.) HultTn
Potamogeton perfoliatus var. richardsonii Benn.