Prairie Gray-stemmed Goldenrod
Solidago decemflora DC. is a tetraploid species native to the Great Plains (see map S. nemoralis). It is distinguished by the following set of traits: Pappus bristles usually exceeding ray floret corolla tubes and bases of disc corolla lobes; disc corolla lobes (0.6–)0.8–1.5 mm; involucres usually 4.6–5.8 mm; cypselae moderately strigose; basal leaves usually not crenate, often linear-oblanceolate. It was treated as a subspecies of S. nemoralis in Flora North America (Semple & Cook 2008 FNA), based in part on the assumption that it was closely related to and relatively recently derived from a diploid population of S. nemoralis (Semple et al. 1990). Recently it was determined that S. nemoralis, S. decemflora and S. nana were members of one of the older lines of evolution in the genus, S. subg. Nemorales (Mackenzie) Semple & J.B. Beck (2021) and it seemed more likely that S. decemflora had a now extinct diploid ancestor that was much older then previously assumed. There are multiple synonyms for this species; S. nemoralis subsp. decemflora (DC.) Brammall ex Semple, S. nemoralis var. longipetiolata (Mack & Bush) E.J. Palmer & Steyerm. refers to the sometimes linear oblanceolate basal leaves produced by the subspecies. Names based on S. longipetiolata do not have nomenclatural priority. Solidago decemflora is known throughout it range to be tetraploid 2n=36.