Whorled rosinweed

Silphium trifoliatum Linnaeus, Sp. Pl. 2: 920. 1753; S. atropurpureum Retzius ex Willdenow; S. laevigatum Pursh

Plants 75–140 cm. Leaves: basal persistent; cauline mostly whorled (in 3s); faces glabrous or sparsely hairy. Paleae puberulent. Ray florets 11–16. Disc florets 35–90. 2n = 14.

Flowering mid summer–early fall. Prairies, meadows, roadsides, along railways; 100–900 m; Ala., Ga., Ill., Ind., Ky., Md., N.Y., N.C., Ohio, Pa., S.C., Tenn., Va., W.Va.