Annuals or biennials, (15-)30-70(-100+) cm. Leaves on proximal 1/2-3/4 of each stem; blades of undivided cauline leaves ovate to orbiculate, margins entire or denticulate, seldom prickly, midribs rarely prickly-setose. Heads usually in corymbiform, sometimes in paniculiform, arrays. Involucres 8-13+ mm. Phyllaries usually erect in fruit. Florets 7-15(-30+); corollas yellow (sometimes streaked with violet), usually deliquescent. Cypselae: bodies pale grayish to whitish or tan, ± flattened, obovate, 3-4 mm, beaks ± filiform, 3-5 mm, faces 5-9-nerved; pappi white, 3.5-4+ mm. 2n = 18. Flowering mostly Jul-Sep. Disturbed sites, abandoned plantings; 10-1000 m; introduced; Ont.; Ala., Calif., Conn., Del., D.C., Idaho, Ill., Ind., Maine, Mass., Mich., Mo., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., Vt., Wash., W.Va.; Eurasia; introduced also in Mexico; introduced or ephemeral nearly worldwide.
From Flora of Indiana (1940) by Charles C. Deam
I can not separate this form of the prickly lettuce from the preceding one [Lactuca scariola] in reports, so I must rely upon the data of the specimens at hand. It has the same habitat as the species and I believe that it is rather infrequent in the state.
Indiana Coefficient of Conservatism: C = null, non-native