Further checking in Ky. is needed for potential transitions to altissima or other variants. However, it is reasonable to treat typical canadensis and typical altissima as generally distinct species (FNA 20; Y, W). S. canadensis is a diploid (2n = 18 versus 36 or 54) with more northern range and earlier flowering, even where sympatric (Pors & Werner 1989; J. Semple, pers. comm.). Typical canadensis differs from altissima in its stems glabrate or sparsely hairy in upper section (versus usually hairy throughout or glabrescent in lower); mid- to upper cauline leaves clearly serrate (versus minutely serrate to entire), usually glabrous or sparsely hairy below (versus densely hairy); inflorescence broadly pyramidal (versus narrow to broad); involucres 1.7-2.5 (3) mm long (versus 2.5-4.5 mm), usually produced in Aug-Sep (versus Sep-Oct); insect galls are usually lacking (versus common). Colls. included here from HENR (KY) and perhaps elsewhere (CARL, FULT & HICK at MUR) have been referred to the relatively hairy var. hargeri Fern., which is diploid but often resembles altissima and deserves further study in Ky. as an intermediate taxon (Semple et al. 2015). That variety is prevalent in some midwestern regions, including most of Mo. (Y; Ladd & Thomas 2015).