Synonyms for Leather Flower (same or very similar meaning)
WordNet sense 1 (scandent subshrub of southeastern United States having large red-purple bell-shaped flowers with leathery recurved sepals):
vase-fine, Clematis viorna, vase vineWordNet sense 2 (woody vine of the southern United States having purple or blue flowers with leathery recurved sepals):
Clematis versicolorFrom the ODE community, based on WordNetadd/edit