Butterfly Bush and Swallowtail

Butterfly Bush (Buddleja davidii)

Beauty and Controversy

The butterfly bush (Buddleja davidii) is a striking deciduous shrub known for its long, fragrant flower spikes that attract a dazzling array of pollinators, particularly butterflies such as the swallowtail and many others. Native to China and parts of Central Asia, this fast-growing plant has become a popular ornamental in gardens worldwide. Its ability to thrive in various conditions, coupled with its vibrant blossoms in shades of purple, pink, white, and even yellow, makes it a beloved feature in pollinator-friendly landscapes. However, despite its beauty and ecological benefits, Buddleja davidii is also a subject of debate due to its invasive tendencies.

A Magnet for Pollinators

Butterfly bush earns its name by being one of the most attractive nectar sources for butterflies, bees, and hummingbirds. The swallowtail butterfly, in particular, is often seen flitting between its blooms, drawn by the abundant nectar reserves. Its long bloom time—from mid-summer to frost—ensures a continuous food source when many other plants have ceased flowering.

Despite its appeal to adult butterflies, however, butterfly bush does not serve as a host plant for caterpillars. This means that while it feeds mature butterflies, it does not contribute to the full life cycle of these species as native plants do. Gardeners looking to support pollinators holistically often pair butterfly bush with native host plants such as milkweed (Asclepias spp.) or spicebush (Lindera benzoin) to ensure both nectar and larval food sources.

The Invasive Debate

One of the biggest controversies surrounding Buddleja davidii is its status as an invasive species in many regions, particularly in the United States and parts of Europe. Due to its prolific seed production and ability to colonize disturbed areas, it has escaped cultivation and spread aggressively in some environments, outcompeting native plants. It thrives along roadsides, riverbanks, and abandoned lots, often forming dense thickets that limit biodiversity.

Several states, including Oregon and Washington, have classified butterfly bush as a noxious weed, restricting its sale and encouraging control efforts. To mitigate its invasiveness, some gardeners opt for sterile or seedless cultivars, such as Buddleja ‘Blue Chip’ or Buddleja ‘Miss Molly’, which offer the same aesthetic and pollinator benefits without the risk of spreading uncontrollably.

Growing and Caring for Butterfly Bush

For those in areas where butterfly bush is not invasive or where sterile cultivars are permitted, proper care can help keep it an asset rather than a liability in the garden:

• Sun & Soil: Prefers full sun and well-drained soil; tolerates poor soil conditions.

• Watering: Drought-tolerant once established; benefits from occasional deep watering in dry periods.

• Pruning: Should be pruned aggressively in late winter or early spring to encourage bushy growth and reduce seed spread.

• Containment: Deadheading spent flowers can help prevent unwanted self-seeding.

Striking a Balance

While butterfly bush is undeniably a beautiful and beneficial plant for adult butterflies and pollinators, its invasive potential means it should be planted with care. In warmer climates it can become more invasive than northern climates. Responsible gardening choices, such as managing seed spread, and incorporating native plants alongside it, can help ensure that butterfly bush remains an ecological asset rather than a potential threat to native ecosystems.