Pluchea sericea is more similar to the segregates than to herbaceous American groups; the delimitations of the genera are not clear. Tessaria was restricted to T. integrifolia Ruiz & Pavón, based on its single functionally staminate flower per head and corolla lobes cut nearly to the base of the limb, by H. Robinson and J. Cuatrecasas (1973). The sister species of T. integrifolia appears to be T. absinthoides (Hooker & Arnott) Cabrera [= Pluchea absinthoides (Hooker & Arnott) H. Robinson & Cuatrecasas]. Both species have inner phyllaries with reflexing tips, alveolate and paleate receptacles, pappus bristles basally united into a thick cup, and other distinctive floral features (G. L. Nesom 1989). It seems likely that the accepted definition of Tessaria may be expanded to two species or more broadly to include P. sericea and the species placed in Berthelotia. Alternately, Berthelotia (including P. sericea) might be accepted at generic rank, coordinate with Tessaria. In any case, it seems likely that P. sericea ultimately will be treated outside a more strictly circumscribed Pluchea.