The Butterfly Bush in Gardening

History

• The Buddleia genus gets its name from an English botanist, Adam Buddle, and the davidii species from its discoverer, Armand David. Found in China, the seed-grown plants first gained favor in Europe as summer lilac for their long flower panicles, which are often shades of lavender with an orange eye. Because of the attraction of butterflies, as well as bees and hummingbirds, to the tiny, fragrant blooms, butterfly bush is the common name most gardeners know.

Characteristics

• Grown as shrubs, butterfly bushes produce their flowers virtually all summer long. The plants are hardy to U.S. Department of Agriculture zone 5 and are so fast-growing that, without yearly pruning, they typically become rangy and weedy looking. At a mature size of as much as 15 feet tall, and almost as wide, the shrubs can outgrow their welcome.

  Despite their hardiness, butterfly bushes are prone to die back to the ground during winter, so late winter pruning is advisable. Because most cultivars so readily reseed, however, it is best to remove the seed heads in the fall, before they mature and add to maintenance, making the shrubs rather unattractive during the winter.

Cultivar Research

• Breeders have developed so many Buddleia davidii cultivars that mislabeled plants are all too common, warns Clemson Extension Cooperative Extension agent Cory Tanner. Despite the many varieties, Cornell University's Peter Podaras notes that, in addition to the awkward shrub size, most cultivars bloom in disappointing pastel shades rather than clear colors.

  In addition to efforts to produce smaller shrubs with better flower color, breeders are also interested in reducing fertility to stop seed production. Finally, the finding that many cultivars carry viral diseases that can cross-contaminate crops has led to interest in using tissue culture to improve species health. Promising new cultivars may be on the horizon, with the work of North Carolina State College of Agriculture and Life Sciences plant breeder Dennis Werner. Lo and Behold Blue Chip, introduced in 2008, is the first of a projected series of compact cultivars that produce few seeds.

Invasive Potential

• The introduction of sterile cultivars is an important and timely development. In 2005, the U.S. Forest Service named butterfly bush the weed of the week and noted its spread throughout much of the country. Oregon banned commerce of all but sterile cultivars of Buddleja davidii in 2010.

  Avoid planting butterfly bushes in your garden if you live in an area where authorities list them as invasive. Even if you haven't had problems with shrubs reseeding in your own yard, trust your state or local officials to know which plants cause problems. Windblown or waterborne seeds may spread butterfly bush to distant locations where they grow unchecked and take habitat from more desirable native species.