The plant known as the butterfly bush, scientifically named Buddleja davidii, is a popular deciduous shrub in gardens around the world. Gardeners favor this plant for its striking, conical flower spikes that bloom throughout the summer season. The vivid color and sweet fragrance of the flowers attract adult butterflies and other pollinators. This widespread appeal has made the shrub a common sight in temperate landscapes.
The Native Range
The butterfly bush is native to central and southwestern China, including Sichuan, Gansu, and Hubei provinces. It is not indigenous to North America or Europe, where it is now commonly found. In its original environment, the shrub thrives in challenging, disturbed habitats.
It grows on mountainous slopes, along rocky streambanks, and in forest clearings, often reaching elevations up to 3,500 meters. This high-altitude habitat explains the plant’s robust, adaptable nature and tolerance for poor soil conditions. The species was first formally documented in 1869 by the French naturalist Père Armand David, for whom the species name davidii is dedicated.
Global Spread and Cultivation
The introduction of the butterfly bush to Western horticulture began in the late 19th century, following explorations by plant hunters in China. Seeds and cuttings were sent to Europe, where the species was first cultivated and quickly gained popularity.
Buddleja davidii is a fast-growing, hardy shrub that adapts easily to various climates. Its ability to tolerate drought, poor or disturbed soils, and a wide range of temperatures made it a resilient option for new gardens. The shrub’s extended flowering period, sometimes lasting from mid-summer into the first frost, ensured its commercial success. Over the past century, extensive breeding programs have developed numerous cultivars, offering a variety of flower colors and sizes to the ornamental plant market.
Ecological Impact Outside its Native Range
Despite its common name and popularity, the butterfly bush presents an ecological challenge when planted outside of its native range. Because it is a non-native species, it frequently lacks the natural predators and diseases that would control its growth in Asia. This absence allows the shrub to grow aggressively and rapidly colonize new areas by producing copious amounts of wind-dispersed, dust-like seeds.
In temperate regions, including parts of the United States Pacific Northwest and the United Kingdom, B. davidii has escaped cultivation and become naturalized. It is classified as a noxious weed in places like Oregon and Washington state, where it out-competes native vegetation along roadsides, railway lines, and riparian areas. This displacement of native plants disrupts the local ecosystem by reducing the food sources available to native wildlife.
The shrub creates an ecological paradox for butterflies: while its nectar is highly attractive to adult butterflies, its leaves are not recognized as a food source by the larvae (caterpillars) of native butterfly and moth species. By displacing native host plants that caterpillars require to survive, the shrub contributes to the decline of native insect populations and the birds that rely on them for food.
Native Alternatives for Pollinator Gardens
Gardeners seeking to support local pollinator populations while providing a nectar-rich display should consider native alternatives that serve as both nectar sources and host plants. Selecting species indigenous to the region provides the full life-cycle support that native butterflies and moths require. These native plants are adapted to local soil and climate conditions, often requiring less maintenance and water than non-native species.
For a summer-blooming shrub, Clethra alnifolia, commonly called Summersweet, offers fragrant flower spikes and is native to much of eastern North America. Another excellent choice is Cephalanthus occidentalis, or Buttonbush, which produces unique spherical flowers highly favored by pollinators and can serve as a host plant for certain moth species.
Perennials like Asclepias tuberosa (Butterfly-weed) provide the necessary host material for Monarch butterfly caterpillars while also supplying abundant nectar for adult insects.