Annuals (perhaps persisting), (15-)30-70(-100+) cm. Leaves on proximal 1/2-3/4 of each stem; blades of undivided cauline leaves usually ± oblong, sometimes ob-ovate to lanceolate, margins denticulate, usually prickly, midribs usually prickly-setose, rarely smooth. Heads in pani-culiform arrays. Involucres 9-10(-12) mm. Phyllaries usually reflexed in fruit. Florets 12-20; corollas yellow, usually deliquescent. Cypselae: bodies pale grayish to tan, ± flattened, oblanceolate, 2.5-3.5 mm, beaks ± filiform, 2.5-4 mm, faces (3-)5-9-nerved; pappi white, (3-)4-5 mm. 2n = 18. Flowering (May-)Jul-Sep(-Oct). Roadsides, disturbed sites; 10-2300 m; introduced; Alta., B.C., Man., N.B., N.S., Ont., P.E.I., Que., Sask.; 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.; Europe; also introduced nearly worldwide. The name Lactuca scariola Linnaeus is evidently illegitimate; it is a superfluous name based on the same type as L. serriola. Plants included here in L. serriola with most leaf blades obovate to lanceolate (not lobed) and lacking prickles on midribs have been called L. scariola subsp. or var. integrata or L. serriola forma integrifolia or L. serriola var. integrata.
Plant: Annual forb to 70 cm, from taproot; herbage with milky sap; stems erect, prickly-bristly Leaves: early leaves sometimes in basal rosette; leaves basal and cauline, alternate, few-many, oblanceolate to obovate, dentate to coarsely lobed, clasping, prickly-bristly on midvein INFLORESCENCE: open; branches often widely spreading; primary inflorescence a head, each resembling a flower; heads ligulate, in flower 4-6 mm wide; involucre in fruit 10-12 mm, cylindric; phyllaries in 2-several series; receptacle naked Flowers: Flowers 14-20; corolla pale yellow; ligules yellow or cream to blue, readily withering Fruit: 6-7 mm (including beak), light to dark brown, rough-hairy, several-veined on each face, unwinged, beak = or > body, slender; pappus 4-5 mm, white, of many bristles, falling separately Misc: Abundant. Weed of disturbed places; < 2000 m.; May-Sep References: J.C. Hickman, ed. The Jepson Manual.W.B. McDougal. Seed plants of Northern Arizona. ASU specimens.