General:
Perennial aquatic herb from a fibrous root; stems much branched, submersed, 30-150 cm long, about 1 mm thick.

Leaves:
Basal leaves lacking; stem leaves linear, 1-3 cm long, about 0.5 mm wide, in nearly opposite pairs, the base expanded for 3-5 mm and more or less sheathing, the margins minutely toothed, tapering continuously to the slender tips.

Flowers:
Inflorescence solitary or a pair of unstalked or nearly unstalked, axillary, unisexual flowers; perianth parts lacking; male flowers with 1-chambered anthers.

Fruits:
Achenes, spindle-shaped, about 3 mm long, smooth.

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

Flower Colour:
Green

Blooming Period:
Late Summer

Fruit/Seed characteristics:
Colour: Green
Present from Summer to Fall

Source:  The USDA

Synonyms and Alternate Names:
Caulinia flexilis Willd.
Najas caespitosa (Maguire) Reveal
Najas flexilis subsp. caespitosa Maguire
Najas flexilis var. congesta Farw.
Najas flexilis var. robusta Morong