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

General:
Perennial, aquatic herb from long rhizomes; stems up to 120 cm long, 1-3 mm wide, unbranched or sparsely branched.

Leaves:
All submersed, linear, thread-like, 5-10 cm long, the lower ones up to 3 mm wide, with 1 vein, the tips round to blunt or notched, firm, dark green, the stipules 2-5 cm long, fused into inflated sheaths, the leaf blades arising close to the tips of the sheaths.

Flowers:
Inflorescence spikelike, the spikes 1.5-7 cm long, interrupted, with 3 to 12 whorls of flowers, the stalks thin.

Fruits:
Achenes, almost globe-shaped, 3.5-4 mm long, 2.5-3 mm wide, widest above the middle, the beaks and keels absent, the surface with fine, ray-like grooves.

Notes:
Many specimens in herbaria identified as Stuckenia vaginata (Potamogeton vaginatus) are, in fact, misidentified specimens of Stuckenia filiformis ssp. occidentalis.