Butterfly bush has a lot to offer our gardens. A long-flowering period, graceful form and dense clusters of fragrant blooms that are intensely attractive to butterflies and hummingbirds.
Most plants available to us are hybrids of Buddleia davidii, a native of China that seeds freely and produces a tremendous range of variations of color and form. Plants prefer full sun and a moist, fertile, well-drained soil.
In our Zone 5 Michigan climate, the shrubby plants perform as a perennial, dying back to the ground in winter, but roots surviving and new growth sprouting again in the spring to reach a height of 5 or 6 feet each summer. In Zone 6 which is warmer, plants are true shrubs and grow larger, up to 15 to 20 feet.
Flowers develop on the new season’s growth, beginning in July and continuing until nighttime temperatures drop consistently below 40 to 45 degrees. The long, fragrant flower clusters are typically 4 to 6 inches in length, although they can be much larger on some of the new hybrids.
Regardless of the climate, most experts recommend cutting plants back to 12 to 18 inches in spring, reducing the overall plant height and keeping the flowers closer together for a greater impact. A light shearing in mid to late June, before buds form, will further increase the flower display.
A few weeks into the blooming period, trim off old flowers. This will reduce unwanted seeding, keep plants looking fresh, and extend strong blooming well into fall.
My favorite of the classic butterfly bush varieties is Pink Delight.
Broad silvery leaves are a perfect complement to clear pink flowers in large clusters, at least two inches across and six to twelve inches long.
Other tried and true selections include Royal Red, with violet red-purple blooms in large panicles similar in size to those of Pink Delight. Black Knight is the deepest navy blue and reputed to be extra hardy. A naturally occurring variety, nanhoensis, has produced a trio of compact selections with smaller leaves and more petite flower clusters in great abundance; Petite Indigo (aka Nanho Blue), Petite Plum (aka Nanho Purple) and Petite Snow (aka Nanho White).
Yellow is a less common color, developed by crossing B. davidii with a less hardy species. Honeycomb, Sungold and Moonlight are forms that capture the color from one parent and hardiness from davidii. Flower form is distinctive, the cluster a series of balls around the stem, rather like a multi-scoop ice cream cone on a stick.
You’ve probably seen advertisements for the amazing rainbow butterfly bush, or a three-in-one, a single shrub with red, white and blue flowers.
This is not an exotic hybrid, nor a hoax. Buddleias root easily from cuttings, and the grower has simply taken three cuttings, one from each of the three colors, and rooted them into a single pot.
Typically one of the plants will crowd out the other two, and your rainbow will eventually become a single color.
The latest trend in breeding has resulted in naturally compact, densely branching forms. They are also sterile, which eliminates unwanted seedlings and keeps plants blooming profusely without the need to trim back spent flowers.
In my garden I have Blue Chip, from the Lo and Behold series; a tidy little plant that grows just 2 feet tall and wide. It dies to the ground each winter but has come back vigorously each year for nearly a decade. Flutterby Petite Blue Heaven has also done well for me, with light blue flowers on 24- to 30-inch plants.
Look for Buzz, Pugster and the new Chrysalis series as breeders continue to refine these excellent garden plants.