This has often been treated as a distinct northern species, especially in former prairie regions (F, W; Ladd & Thomas 2015), but there may be some intergradation with typical cannabinum along its southern borders. Herbarium specimens are often impossible to assign (Y), and variety status is often preferred (Cr, DiTomasso et al. 2009) or even complete combination (Y, J, K). Although colls. from FULT (R. Athey), HICK (MUR), MCRA (R. Athey), OLDH (DHL), WARR (WKY) and elsewhere in Ky. have been referred to sibiricum, the presence of this taxon here remains uncertain. More definitive studies in adjacent states indicate that sibiricum is largely restricted to the cool temperate zone and boreal transition, as in n. Mo. (St), n. Ohio (Andreas & Cooperrider 1979), n. W.Va. and n. Va. (W). Based largely on F and St, sibiricum differs in its mid-stem leaves with shorter petioles (0-4 mm versus 2-10 mm) and more rounded to cordate bases (versus cuneate to rounded), greener small bracts in inflorescence (herbaceous versus scarious), flowers usually more yellowish (milky versus greenish), shorter and less curved follicles when fully grown (ca. 4-10 cm versus 12-20 cm), and shorter hairs on seeds (ca. 0.8-2 cm versus 2-3 cm).