General:
Annual or biennial herb from a taproot; stems erect, branched above, usually solitary, glabrous or sometimes coarsely stiff-hairy, exuding milky juice when broken, 0.3-2.5 m tall.

Leaves:
Basal leaves lacking; stem leaves alternate, entire or toothed to pinnate, 10-35 cm long, 1.5-12 cm wide, triangular-shaped or narrowed at the base.

Flowers:
Heads with strap-shaped flowers, numerous in a narrow, elongate inflorescence; involucres 10-15 mm tall; involucral bracts lanceolate, graduated in 4-5 series, often purplish at the tip, glabrous; ray flowers yellow, 13-22.

Fruits:
Achenes blackish, flat, median nerve on each face, 4.5-6.5 mm long including the slender beak which varies from 1/2 as long to as long as the body; pappus white.

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:
Lactuca canadensis var. canadensis L.
Lactuca canadensis var. integrifolia (Bigelow) Torr. & Gray
Lactuca canadensis var. latifolia Kuntze
Lactuca canadensis var. longifolia (Michx.) Farw.
Lactuca canadensis var. obovata Wieg.
Lactuca canadensis var. typica Wieg.
Lactuca sagittifolia Ell.
Lactuca steelei Britt.