Silphium asteriscus Linnaeus var. latifolium (A. Gray) J.A. Clevinger. Phen: Jul-Sep. Hab: Woodlands, roadsides. Dist: VA, WV, and KY south to GA and LA.
Origin/Endemic status: Endemic
Taxonomy Comments: This taxon appears to occasionally intergrade with S. integrifolium in the western edge of its range, and more commonly intergrade with S. asteriscus var. trifoliatum in the Interior Plateau and Cumberland Plateau. However, in the broad core of its range (spanning a region of AL, TN, and KY) populations of S. asteriscus var. latifolium are morphologically consistent and readily recognizable, with large leaves uncharacteristic of both S. integrifolium and S. asteriscus var. asteriscus. Some recent authors have chosen species status, under the name Silphium glabrum. The taxonomy and map are very speculative.
Synonymy: = Silphium glabrum Eggert ex Small – S, Tn; = Silphium laevigatum Pursh – RAB; = Silphium trifoliatum L. var. latifolium A.Gray – C, F, G, K1, SE1, Perry (1937); < Silphium asteriscus L. – Va; < Silphium asteriscus L. var. latifolium (A.Gray) Clevinger – FNA21, K3, K4; ~ Silphium confertifolium Small; < Silphium trifoliatum L. – W