Solidago ontarioensis (Ringius) Semple & Peirson is native to calcareous and basaltic rocks on shorelines in Ontario and Michigan. Solidago ontarioensis is similar to S. glutinosa, but has usually taller involucres and larger shoots have a more open inflorescence with longer branches; cypselae are moderately to densely strigose proximally and distally. The species was treated as Solidago simplex var. ontarioensis (Ringius) Ringius by Semple & Cook (2006 FNA) and included in ssp. randii. The species is tetraploid 2n=36 throughout its range (Peirson et al. 2012).
Semple et al. (2019) presented a multivariate analysis of all 13 species of S. subsect. Humiles. Solidago ontarioensis was included in the analyses of all species, in the analyses of just the 6 species native to mid western and northeastern US and adjacent Canada, and in the analysis comparing just S. glutinosa and S. ontarioensis. In the 12 and 11 species analysis, specimens of S. ontarionensis did not form a well supported group a posteriori. In the 6 species analyses, the S. ontarioensis group held together with much more support (82% and 91% correct placement a posteriori). In the two species analysis, the S. ontarioensis group held together with 91% correct placement a posteriori).