- Deciduous or semi-evergreen shrub, large, 8-12 ft (2.4-3.7 m) high, or taller, unkempt, usually killed to the ground in colder areas. Leaves opposite, simple, ovate-lanceolate to lanceolate, 10-25 cm, 2.5-7.5 cm wide, acuminate, cuneate, serrated margin, gray-green to dark green above, tomentose beneath. Flowers small, fragrant, usually borne in spike-like slender, dense, 10-25 cm long terminal clusters, often lilac colored with orange at the opening. Blooms in summer.
- Full sun, easily grown, almost weed-like. Prune in early spring to control growth and encourage large flowers which are borne on new growth. Remove spent clusters to sustain flowering. Butterflies often visit flowers.
- Hardy to USDA Zone 5 Native to China. Many cultivars available.
- Caution: It has naturalized in Great Britain, New Zealand, and many parts of the U.S. It is often considered a weed (see below). In 2010 the Oregon Department of Agriculture prohibited the sale of non-approved selections of Buddleja davidii within the state of Oregon. Approved sterile cultivars of Buddleja are not regulated under this ruling.
- Buddleia: after the Rev. Adam Buddle (1660-1715). davidii: after Armand David who discovered the species.
- Oregon State Univ. campus: south of entrance to Milam Auditorium
T. Anisko and U. Im published an article entitled, Beware of Butterfly Bush, [Amer. Nurseryman 194(2):46-49, July 15, 2001]. In it they point out the weed capabilities of B. davidii, recalling that it was introduced into Great Britain at the end of the 19th century, and by the middle of the 20th century it had thoroughly naturalized the wastelands of southern England. Now it is listed among the top 20 invasive weeds in England. Anisko and Im studied seed production of a number of Buddleia taxa at Longwood Gardens in southern Pennsylvania. They found large differences in the amount of viable seed produced by B. davidii selections. For example, culitvars 'Summer Rose' and 'Orchid Beauty' produced 20 times fewer viable seeds than 'Potter's Purple' and 'Border Beauty'. A single flower cluster of 'Potter's Purple' was found to produce over 40,000 seeds. Some Buddleia species and hybrids produced fewer viable seeds than B. davidii and likely have lower potential for escaping gardens and colonizing natural areas. The authors encouraged gardeners to deadhead or prune plants in the fall to eliminate the chance of seed dispersal, they are aware, however, that this could increase the risk of cold injury to the plants.
Note: The Oregon Department of Agriculture had identified Buddleia as a noxious weed which prevented the transport and sale of the genus in Oregon. This was ruling amended in 2009 so as to permit approved, seedless butterfly bush cultivars to be propagated, transported, or sold in Oregon. SEE https://www.oregon.gov/ODA/programs/NurseryChristmasTree/Pages/ButterflyBush.aspx