The butterfly bush (Buddleia, most commonly Buddleia davidii or its hybrids), is a popular garden shrub renowned for attracting pollinators. This fast-growing plant produces long, conical clusters of fragrant flowers that act as a magnet for butterflies and hummingbirds throughout the summer. While the plant’s appeal is often associated with wildlife attraction, the spectrum of colors available is surprisingly broad, extending far beyond the typical purple.
The Dominant Color Spectrum
The traditional color palette centers on the cool side of the spectrum, encompassing purples, blues, and magentas. These hues are native to the original species and represent the most common selections found in gardens today. Cultivars like ‘Black Knight’ produce flower spikes of such a dark, rich violet that they often appear almost black, providing a dramatic contrast against the plant’s silvery-green foliage.
Varieties such as ‘Blue Horizon’ or ‘Adonis Blue’ offer flowers that present as a true indigo or violet-blue, representing the closest shades to a genuine blue available in the genus. The anthocyanin pigments responsible for this color are sensitive to soil pH, which can influence the exact shade the flower displays. Pink and magenta varieties, like ‘Pink Delight,’ round out this dominant group with vibrant, rose-pink flower spikes that retain a purple undertone.
The flowers are not uniformly colored; each tiny floret often features a contrasting “eye,” typically an orange or yellow center. These traditional, full-sized cultivars generally reach heights of six to ten feet, forming large, arching shrubs that serve as excellent background plants. The dominance of this color range is due to the natural genetic makeup of Buddleia davidii, making these shades the easiest to reproduce through traditional breeding.
Exploring Uncommon and Novel Hues
Beyond traditional blues and purples, modern hybridization efforts have introduced colors once rare or non-existent in the butterfly bush. These novel hues include pure whites, yellows, and red shades, often requiring complex cross-breeding with other Buddleia species. The color red remains a challenge for breeders because the plant’s chemical structure does not naturally produce the true scarlet pigments found in many other flowers.
The closest shade to red is represented by cultivars such as ‘Miss Molly,’ which produces deep, saturated sangria-red or magenta-red flowers. This intense coloration is an achievement, though the hue often shifts toward a more cerise-purple in cooler climates. White varieties, like ‘White Profusion,’ are widely available and display pure white flowers that feature a yellow eye in the center of each floret.
Yellow and orange hues result from crossing Buddleia davidii with the South American species Buddleia globosa to create Buddleia x weyeriana hybrids. Cultivars like ‘Sungold’ or ‘Honeycomb’ exhibit a golden-yellow color, but their flower clusters often form smaller, more rounded balls instead of the characteristic long, conical spikes of the davidii species. These novel colors highlight the ingenuity of breeders in expanding the available palette despite the genetic limitations of the genus.
Linking Color to Cultivar Selection
The choice of flower color often dictates the overall growth habit and size of the plant selected. Older cultivars, which primarily carry traditional purple, blue, and white colors, tend to be the largest and most vigorous, often maturing into shrubs that can reach up to ten feet in height and spread. These varieties, exemplified by ‘Black Knight’ and ‘White Profusion,’ require significant space and annual hard pruning to maintain their shape and encourage prolific summer blooming.
Conversely, recently developed cultivars, including those in novel red and yellow shades, are frequently bred for a more compact size. ‘Miss Molly,’ with its dark red flowers, typically grows four to five feet tall, making it a medium-sized shrub suitable for smaller gardens or mixed borders. The smallest selections, such as the dwarf ‘Lo & Behold’ series, are available in blue, pink, and white, and often stay under three feet tall.
This correlation between color and size is a result of intentional breeding to address invasiveness concerns associated with the original species. Many newer, compact cultivars, especially those bearing novel colors, are bred to be nearly sterile, producing little viable seed. Selecting a contemporary cultivar based on its specific color often means acquiring a plant with a smaller, more refined, and non-seeding growth habit.