Annuals or biennials, (15-)75-200(-300+) cm. Leaves on proximal 2/3-3/4 of each stem; blades of undivided cauline leaves ovate to lanceolate, margins entire or denticulate, midribs sometimes sparsely piloso-setose. Heads in paniculiform arrays. Involucres 7-12+ mm. Phyllaries usually reflexed in fruit. Florets (15-)20-30(-50+); corollas bluish or whitish, sometimes yellowish, seldom deliquescent. Cypselae: bodies brown (often mottled), ± compressed-ellipsoid, 4-5+ mm, beaks ± stout, 0.1-0.5+ mm, faces (4-)5-6-nerved; pappi ± fuscous, 4-6+ mm. 2n = 34.
Robust, leafy-stemmed annual or biennial, 6-20 dm, glabrous, or the lvs hairy on the main veins beneath; lvs pinnatifid or occasionally merely toothed, 10-40 נ4-20 cm, sometimes sagittate at the base; heads numerous in an elongate, rather narrow, paniculiform infl, often crowded, with 15-34(-55) bluish to white or occasionally yellow fls; invol 10-14 mm in fr; achenes 4-5.5 mm, thin-edged, prominently several-nerved on each face, tapering to a beakless or shortly stout-beaked tip; pappus light brown; 2n=34. Moist places; Nf. to B.C., s. to N.C. (chiefly in the mts.), Ill., Colo., and Calif. (L. spicata, misapplied) An apparent hybrid with no. 3 [Lactuca canadensis L.] has been called L. حorssii Robinson.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
This is our largest species and normal size specimens range from 6-10 feet high. It is a woodland species, preferring rather moist, rich soil. It is rather frequent in the northern part of the state where its flowers are usually cream color. In the southern part of the state it becomes infrequent. Throughout its range it is also found along roadsides.
[Variety integrifolia] is much smaller in stature and very local. Its habitat is the same as that of the species.