Silphium trifoliatum Linnaeus var. latifolium A. Gray in A. Gray et al, Syn. Fl. N. Amer. 1(2): 241. 1884; S. confertifolium Small; S. glabrum Eggert

Plants 50–150 cm. Leaves: basal persistent or caducous; cauline mostly opposite; faces glabrous or sparsely hairy. Paleae puberulent. Ray florets 12–17. Disc florets 35–130.

Flowering mid summer–early fall. Fields, roadsides, disturbed areas; 100–900 m; Ala., Ga., Ky., La., Miss., N.C., S.C., Tenn., Va., W.Va.

Silphium confertifolium has persistent basal leaves and a diminutive stature that is due to environmental variation; it is best included in S. asteriscus var. latifolium.