Petradoria Nutt. is a monotypic genus of small, herbaceous perennials native to western North America. The genus has incorrectly been included in Solidago but differs in having a taprooted wood caudex and distinctive leaf anatomy. Lane et al. (1996) showed that the on the basis of cpDNA RFLP, Petradoria was phylogenetically close to the true goldenrods with a number of other genera more closely related. Zhang (1996) obtained the same results in his cpDNA RFLP study of the goldenrods.