3. Lactuca canadensis Linnaeus, Sp. Pl. 2: 796. 1753.
Lactuca canadensis var. latifolia Kuntze; L. canadensis var. longifolia (Michaux) Farwell; L. canadensis var. obovata Wiegand; L. sagittifolia Elliott
Biennials, (15–)40–200(–450+) cm. Leaves on proximal 1/2–3/4 of each stem; blades of undivided cauline leaves oblong, obovate, or lanceolate to spatulate or lance-linear, margins entire or denticulate, midribs sometimes sparsely pilose. Heads in ± corymbiform to paniculiform arrays. Involucres 10–12+ mm. Phyllaries usually reflexed in fruit. Florets 15–20+; corollas bluish or yellowish, usually deliquescent. Cypselae: bodies brown (often mottled), ± flattened, elliptic, 2.5–3.5 mm, beaks ± filiform, 1–3 mm, faces 1(–3)-nerved; pappi white, 5–6 mm. 2n = 34.
Flowering Jun–Oct. Roadsides, swamps, salt marshes, thickets; 0–2200 m; B.C., Man., N.B., N.S., Ont., P.E.I., Que., Yukon; Ala., Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico; Central America; Eurasia.
