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. Flowering Jul-Oct. Swamps, stream banks, woods; 900-1500 m; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Calif., Colo., Conn., Del., D.C., Idaho, Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mont., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Oreg., Pa., R.I., S.Dak., Tenn., Utah, Vt., Va., Wash., W.Va., Wis., Wyo. The type of Lactuca terrae-novae Fernald is probably conspecific with that of L. biennis. The type of L. biennis may be conspecific with that of L. floridana.
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.