1. Lactuca biennis (Moench) Fernald, Rhodora. 42: 300. 1940.
Sonchus biennis Moench, Methodus, 545. 1794
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.
