Helianthus verticillatus Small. Phen: Aug-Oct. Hab: Seasonally wet to moist calcareous prairies. Dist: Nw. GA, ne. AL, w. TN, and n. MS; disjunct in sw. VA). The species has become a bit popular (niche market) as an ornamental and may be expected to be encountered outside its (admittedly poorly understood) native range.
Origin/Endemic status: Endemic
Taxonomy Comments: This taxon is a species, not a hybrid; its morphological characteristics alone (with its unique whorled leaves) make the hybrid status suggested by Cronquist (1980) ("a hybrid of H. angustifolius with either H. eggertii or H. grosseserratus") implausible. See Matthews et al. (2002) for additional information. Moore, Siniscalchi, & Mandel (2021) analyzed the genetic diversity of the species.
Synonymy: = FNA21, K3, K4, S, Tn; = Helianthus ×verticillatus E.Watson (pro sp.) – C, K1, SE1; = n/a – F