Both Buddleja and Acantholimon are considered which level of classification?
Acantholimon Acantholimon (prickly thrift) is a genus of small flowering plants within the plumbago or leadwort family, Plumbaginaceae. They are distributed from southeastern Europe to central Asia and also in South America, but also cultivated elsewhere in rock gardens.
Buddleja alternifolia 'Argentea' Buddleja alternifolia 'Argentea' is regarded by some as one of the best "Buddleja" cultivars.