Circumscription of S. asteriscus L. (? = S. scabrum Walt.) has varied; see also notes under asperrimum and glabrum, which have also been combined in some past treatments. S. trifoliatum may just be a northern segregate within this complex (FNA 21): S. asteriscus var. trifoliatum (L.) J.A. Clevinger. It occurs mostly in the Interior Low Plateaus and the valleys of Appalachian regions. Typical astericus (Sm) has some opposite leaves below the inflorescence; in trifoliatum leaves are mostly in whorls of 3 (4), but sometimes opposite and rarely even alternate. Its leaves are often elliptic (versus just lanceolate); plants generally have rougher, scabrous or hispid pubescence (versus scabrous or, especially on stems, glabrous); heads tend to have more numerous, smaller rays. Typical asteriscus has a southeastern range, centered on the eastern Piedmont (RAB, W); it has often been reported as far west as e. Tenn., Ala. and Miss. (Cr, Sm)., but there has much confusion with other taxa. There are a few reports of typical asteriscus from Ky. (Harvill 1941; BA, FNA 21), but no verified colls. are known. Plants mapped here as trifoliatum do vary considerably, sometimes with leaves mostly opposite, and often with rougher pubescence in western regions. Some eastern plants have been referred to var. latifolium Gray (F), but that name appears now to be a synonym of S. glabrum (Cr, FNA 21; G. Nesom, pers. comm.). There has been no clear separation of smooth versus hairy segregates of trifoliatum in Ky., after removal of glabrum, and records are combined here pending further analysis. Like some other species of Silphium, trifoliatum is often browsed by deer, making seed production dofficult in nurseries or suburban gardens.