I think one is I. Germanica, a real oldie collected by Linneaus in 1753. [Dark purple falls, med. purple stds, bitone, white beard with some yellow nearer throat.] It can stand so much the environment can dish out. I suppose that is why it has endured. I would have to vote for it as an extremely hardy one. There is even a rhizome near a former factory here, been mowed, had building pieces on it when the building was taken down, had a scraper go over it cleaning up building scrap, yet it had one stalk this May!
