This diploid (2n = 40) has a fragmented range around the southern Appalachians, but concentrated in rocky hills rather than the central mountains (K). It appears closely related to muticum but suggests a transition to the incanum group. P. curvipes differs from muticum as follows (W): petioles usually 3-15 mm long (versus 0-2 mm); inflorescence corymbose, loose, the branches apparent (versus capitate, tight, the branches within the clusters not apparent). It has been recently discovered in Ky. for the first time by V. Voelker (NP), with coll. from a roadside in MUHL (APSC). The species is also known in north-central Tenn. within 20 miles of Ky. (Ch+).