Multivariate analysis of 11 quantitative morphological characteristics of 177 individuals of the Solidago nemoralis complex supports recognition of two subspecies. In a cluster analysis, two groups were immediately obvious (corresponding approximately to ssp. decemflora and ssp. nemoralis); within the ssp. nemoralis cluster, diploids and tetraploids tended to cluster separately. Discriminant analyses were performed on two and three a priori groups. The prairie and open savannah race ssp. decemflora could be distinguished from the eastern ssp. nemoralis son the basis of corolla lobe length, ray floret pappus length, numbers of disc florets, involucre height, and the lengths of the disc corolla, disc corolla limb, and disc floret pappus. Capitulescence form was found to be plastic and of limited taxonomic value. Plants with elongated ascending lower capitulescence branches (elm tree shaped) occurred throughout much of the range of ssp. nemoralis; these have been treated previously as var. or ssp. haleana, but are placed in synonymy. A late glacial and postglacial history of S. nemoralis is hypothesized. In a second set of analyses, small samples of S. nemoralis, S. californica, and S. sparsiflora were compared. Based on the floral characters used, the two subspecies of S. nemoralis differed to a greater degree than S. californica and S. sparsiflora differed from each other. The latter two differed from each other on vegetative traits more so than did the two subspecies of S. nemoralis. The need for a larger study of S. californica, S. sparsiflora, S. velutina, and related taxa was indicated.
