Solidago fallax

Big-toothed Canada Goldenrod

Solidago fallax (Fernald) Semple was treated as part of S. lepida or S. canadensis by various authors since it was first described as S. lepida var. fallax Fernald in 1915.  Semple and Cook (2006 FNA) treated the species as S. lepida subsp. fallax (Fern.) Semple.  More recently, Semple (2013) proposed treating the taxon as a separate species and Semple et al. (2013) presented statistical support for recognizing the species and it two varieties.  The species is native to eastern Canada.

Solidago fallax has broader mid and upper leaves than those of S. bartramiana (synonym: S. brendae; Semple 2023).  Both species have inflorescences that are usually more leafy compared to those of S. canadensis.  The leaves usually have large coarse serrations along the mid and upper stem leaf margins.  Involucre height is greater in S. fallax (diploid 2n=18, tetraploid 2n=36, and hexaploid 2n=54) than in S. canadensis (diploids only) with higher ploidy levels having larger involucres. Semple and Chmielewski (2022) reviewed published counts for S. fallax and mapped the locations of all counts. Solidago fallax can be confused with likely introduced hexaploid plants of S. lepida occurring near the Québec-New Brunswick border.

Semple (2013) recognized two varieties differing in the density of hairs on the stems and leaves:

• var. fallax  (smooth lower to mid stem; leaves smooth)
• var. molina (very sparsely to moderately hairy lower to mid stem; leaves somewhat hairy)