The genus of the so-called butterfly bushes, Buddleja, has done remarkably well for itself. Its 150-plus species occur throughout Asia (where it’s geographically centered), in the higher elevations of South Africa and from western North America south to Tierra del Fuego. The spelling of the genus has long been muddled; the American rendition, Buddleia, has lost favor among the pundits.
From Weed to Garden Splendor
Recent studies have shown many Buddleja species exhibit a highly efficient use of soil nitrogen coupled with a highly efficient system of photosynthesis. These attributes paired with simple fecundity (a typical flower head of B. davidii ‘Potter’s Purple’ will release 40,000 fertile seeds each year) have resulted in a blitzkrieg of naturalization in temperate climates outside its natural range. In a mere 50 years since its introduction in England, B. davidii has become one of that country’s most wide-ranging weeds. Yet with caution and proper selection of species and cultivars, buddlejas can still be brought into the garden setting with a clean conscience.
Though this genus is chiefly associated with its fragrant, butterfly-attracting flowers, I’ve long maintained that it should be considered as much for its foliage. All the species possess paired leaves that are retentive during the winter and terminal panicles that bloom on the current year’s growth. All except B. alternifolia, that is. It blossoms on the previous year’s wood. I’ve not yet had the opportunity to visit the native haunts of this species, as Reginald Farrar did in the early 20th century. Today the clever and cynical Farrar remains an enigma, but his observations of plants are often spot on. Of B. alternifolia, he wrote, “in blossom embodying an elegant waterfall of purple, in foliage a doppelganger of an old olive.”
As a general rule, species that blossom on the current year’s wood will do well in Zones 6 through 10, although B. davidii is safely hardy to 10