General:
Perennial, tufted herb from long, creeping rhizomes; stems triangular, with smooth edges, 15-120 cm tall, equalling the leaves.

Leaves:
Sheaths tight, short; blades flat, well distributed along the stem, 3-7 mm wide, the lower ones slightly reduced.

Flowers:
The terminal spikes 1 to 3, short-stalked, with male flowers, the lower spikes 2 to 7, with female flowers, unstalked or with short stalks, 3-14 cm long, erect; bracts subtending the spikes leaflike, sheathless, the lower ones longer than the inflorescence, the upper ones reduced.

Fruits:
Perigynia egg-shaped, 2-3.6 mm long, 1.3-2.3 mm wide, brownish-green, 3-angled, the angles rounded, smooth to somewhat wrinkled, 2-nerved, the beaks entire; female scales egg-shaped, shorter than or about as long as the perigynia, often shortly awn-tipped, brownish-red to blackish, with lighter 3-nerved centres, with translucent margins; stigmas 2; achenes lens-shaped, granular, 1.4-1.8 mm long. Two subspecies may be recognized in BC 1. Male spikes 2 to 3; plants generally more than 20 cm tall; plants more common southward ssp. aquatilis 1. Male spike 1; plants generally less than 20 cm tall; plants more common northward ssp. stans (Drej.) Hult.

Source:  The Illustrated Flora of British Columbia