The Butterfly Bush, Buddleia davidii, is a common ornamental shrub prized for its long blooming season and dramatic, cone-shaped flower clusters. It earned its popular name due to its remarkable ability to attract numerous butterflies, creating a vibrant spectacle. Originating in China, it was introduced globally as a garden fixture and quickly became associated with pollinator-friendly gardening. While gardeners often observe bees flocking to the blossoms, the actual role of the Butterfly Bush for bees and other native insects involves a more complex biological and ecological reality.
Why Bees Visit Butterfly Bush
The observation that bees visit Buddleia davidii is accurate and easily explained by the plant’s robust advertising strategy. The dense, showy flower clusters, often displaying vivid purple, pink, or white hues, provide a powerful visual signal highly attractive to foraging insects. These large inflorescences also act as substantial landing platforms, making the flowers easily accessible to different bee species, from large bumblebees to smaller solitary bees. Furthermore, the flowers emit a strong, sweet floral scent, an olfactory cue that guides bees to the resource from a distance. This combination of visual targets and potent fragrance successfully draws in various pollinators, including European honeybees and native bumblebees.
Nectar Quality and Nutritional Value for Pollinators
Despite the high numbers of bees observed on the flowers, the nutritional reward offered by the Butterfly Bush is often insufficient for supporting healthy bee development and colony maintenance. The plant produces copious amounts of nectar, which primarily contains sugars to fuel the bee’s flight and immediate energy needs. However, the composition of this nectar and the accompanying pollen presents a biological challenge. Bees require high-quality pollen rich in protein, derived from essential amino acids, to successfully rear brood and maintain colony health. Scientific analysis of the pollen and nectar from Buddleia davidii has often shown significantly lower concentrations of these necessary amino acids when compared to native flora. The resulting pollen collected lacks the complex nutrients needed for larval growth and robust immune function. The abundant sugary nectar essentially functions as “empty calories,” providing short-term energy without the necessary building blocks for long-term health. A bee colony requires a complete, balanced diet with approximately 20–25% protein content for optimal survival and growth, a requirement that this nutritionally poor forage struggles to meet.
Ecological Impact: Non-Native Status and Invasiveness
Beyond the individual bee’s diet, the Butterfly Bush presents a broader ecological concern due to its status as a non-native species in many regions, including North America and Europe. Originating in China, Buddleia davidii is categorized as invasive in numerous areas because of its aggressive growth and prolific reproduction. A single plant can produce up to a million tiny, wind-disposed seeds, allowing it to rapidly colonize disturbed sites, roadsides, and open woodlands. This vigorous growth displaces native plants that would naturally occupy those spaces.
The displacement is particularly damaging to native insect populations because the shrub does not support the full life cycle of many species. While adult butterflies consume the nectar, their caterpillars cannot feed on the leaves of the Butterfly Bush, meaning it is not a host plant. By replacing native flora, Buddleia davidii removes the necessary host plants that native caterpillars and other insect larvae rely on for survival, leading to a net reduction in biodiversity and disrupting the foundational food web for birds and other wildlife.
Native Plants That Provide Superior Bee Forage
Gardeners who wish to genuinely support native bee populations and ecosystem health should opt for native plants that offer a complete nutritional profile. Selecting species native to the local region ensures the forage is rich in the specific sugars, amino acids, and lipids that local bees have evolved to rely on. These plants provide a high-quality food source that supports both adult foragers and healthy brood development.
Excellent Native Alternatives
Excellent alternatives known for providing superior bee forage include:
- Native Milkweeds (Asclepias species), which are host plants for Monarch butterflies and offer abundant nectar.
- Native Asters and Goldenrods (Solidago species), which are essential for providing late-season pollen and nectar vital for bees preparing for winter.
- Bee Balm (Monarda species).
- Coneflowers (Echinacea).
- Mountainmints (Pycnanthemum species), which are recognized for their high-quality nectar and pollen rewards.