Mapping is provisional due to much past confusion with glabrum. S. integrifolium is a widespread, largely midwestern species, but virtually unknown east of Ind., w. Ky., w. Tenn. and Ala. except where it has been included in "wildflower" plantings (K, W). It is sensitive to browsing by deer (Anderson et al. 2001). The species is best distinguished by its relatively compact inflorescences, with strictly opposite branches and relatively large heads (with usually12-36 rays versus 6-14 in the asteriscus complex), together with its strictly opposite, sessile to subsessile, broad-based, usually subentire and often slightly clasping leaves (Cr, FNA 21). However, its circumscription deserves further revision; segregates remain uncertain, and there has been much confusion with other species. Note that 2n = 14 in most or all Silphium species, and hybrids are often suspected (Cr, FNA 21, Y; Jessee & Yatskietych 2011). Most or all colls. of integrifolium from Ky. are referable to var. integrifolium, which is more or less pubescent. More hairy forms have sometimes been misidentified as S. radula Nutt. (Ozarkian to Texan) or S. asteriscus L.; see notes under trifoliatum. A few less hairy colls. from Ky. and Tenn. have been referred to the more western var. laeve Torr. & Gray (= S. speciosum Nutt or, perhaps with priority, S. trachopus Raf.), which is relatively glaucous and tends to have larger heads. However, these colls. may be just be misidentified glabrum (e.g. W.H. Martin 7-22-78 from LOGA at EKY); see also BA and J. Also, Harvill (1941) reported var. deamii Perry (from GRAV), which has glandular phyllaries (known mostly from Ill.), and var. gattingeri Perry (based on the coll. from SIMP at KY-Agr.), which has glabrous stems; but the latter (with types at GH) should probably be included in glabrum. Records from JEFF (APSC ex DHL) and perhaps HARD (NP from Fort Knox) appear to be based on verified native plants. The outlying record from JOHN (USCH; see SERNEC) appears to be typical integrifolium, but this was just a student coll. from "Paintsville, Kentucky"; possibly, this was an error or a cultivated plant. Records that appear to be from plantings or sowings are excluded: e.g. from FAYE (Center Parkway Pond, JC).