Similar to P. coriacea but slightly smaller and stouter, usually with a solitary rosette and sharply toothed leaves. Umbels larger with the collar of bracts more deeply lobed. Chile and Argentina, mainly on Volcan Llaima and Volcan Longuimay, on volcanic ash slopes, screes and bare soil at 1800-2000m. Argentinian plants are said to be intermediate between the two species, so P. volcanica may not remain at full specific rank. Often associated with ants which rest beneath the plant and defend it from predators, gaining in return a copious nectar supply.