These rather poorly known plants occur locally in thin woods on dry calcareous soils of ne. Ky., disjunct from their main range in the Ridge and Valley region of Tenn., N.C., Ga. and Ala. (Buckley coll. at NY); early records from Ohio can be transferred to T. barbinode var. garmanii. Leaf shapes appear to vary between these ranges, and some genetic differentiation may be expected (as in Solidago harrisii). The plants in Ky. may be genetically distinct (D. Estes & A. Floden. pers. comm.), but there do not appear to be clearcut morphological differences. T. pinnatifidum can be distinguished from chapmannii and barbinode as follows, but this can be difficult. Leaves are relatively deep green (versus yellowish- or grayish-green), usually glabrous except for sparse short hairs along veins below (versus glabrous or more widely hairy), 3-4-ternate (versus 1-3-ternate), with numerous ultimate pinnatifid segments ca. 5-10 x 1-3 mm in size (versus serrate to laciniate segments ca. 8-30 x 5-20 mm). Bractlets are mostly longer (ca. 3-6 mm versus 1-4 mm). Flowers are generally white when fresh (versus creamy-white to bright yellow), but can change to "yellowish-tan" in older colls. (W). Fruits are mostly 3-4 x 2-3 mm with relatively narrow wings and often puberulent (versus 3-6 x 2-4 mm with some relatively broad wings and glabrous). There are three colls. of C.W. Short (NY) that appear to be pinnatifidum from "Barrens of Ky." in 1840 and 1842, but the location is unknown--did he mean the extensive western "barrens" or grassland in the Knobs? Excluded records here include: Short 1840s from HARD (FI), which appears to be chapmanii; and W. Overbeck15 Aug 2014 (BEREA) from LEE, which is correctly identified but was reportedly (pers. comm.) established from transplanted seed.