South Carolina Goldenrod
Solidago austrocaroliniana Semple & Nelson is the recently described new species known from a single collection C.R. Bell 8499 (NCU) from Union Co., South Carolinia. It is the rarest species in S. subsect. Humiles and differs from S. arenicola, which is similar in general appearance, in having smaller involucres (5-6 mm) and blooms in May-June. Like other species in subsect. Humiles, S. caroliniana has resinous phyllaries and inflorescences parts. No other species of S. subsect. Humiles occurs in the “upcountry” of South Carolina. Solidago kralii has been collected in Aiken Co., South Carolina near I-20 only a few miles from long known populations near Augusta, Georgia on the "fall line" at the edge of the Piedmont. Solidago plumosa is known only from one population in North Carolina. Species of S. subsect. Humiles in the southeastern US are rare to very rare and all are potentially threatened due to such limited distributions.
The chromosome number is unknown, but it may be diploid based on involucre size.
Semple et al. (2019) presented a multivariate analysis of all 13 species of S. subsect. Humiles. Solidago austrocaroliniana could only be included in the as an unassigned specimen a posteriori. In the 12 and 11 species analysis the single specimen of S. austrocaroliniana was not assigned to any species with high probability. In the canonical analysis for the 4 species native to the southeastern US, the one specimen of S. austrocarolina came out near S. arenicola but outside the 95% confidence limits for that species.