General:
Perennial aquatic herb from a fibrous root; stems solitary, sparingly branched.

Leaves:
Stem leaves in whorls of 3 (below) and 4 or 6 (above), lanceolate, 2-3.5 cm long, 2-5 mm wide, minutely sharp-toothed.

Flowers:
Inflorescence 2- to 4-flowered (male) or 1-flowered (female); flowers axillary, long-stalked, one per stalk; petals 3, white, egg-shaped, 8-11 mm long; sepals 3, greenish, egg-shaped, 3-5 mm long; stamens 9.

Fruits:
Capsules, cylindric or egg-shaped; seeds several.

Notes:
Only male plants known in N America.

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:
Anacharis densa (Planch.) Victorin
Elodea densa (Planch.) Caspary
Philotria densa (Planch.) Small & H. St. John