Ask a Master Gardener: All about the “butterfly magnet”

In the world of flowering shrubs, few plants can match Buddleia for the ability to attract butterflies.

Given the common name of butterfly bush, many gardeners refer to it as a "butterfly magnet," since it is rarely seen in bloom without butterflies present. Given its recent rise in popularity due, in part, to the introduction of attractive new cultivars, the National Garden Bureau has chosen Buddleia as its flowering shrub to promote in 2024.

Buddleia carries the scientific name of Buddleia davidii and is a member of the Scrophulariaceae (or figwort) family of flowering plants. Native to central China and Japan, the genus was named in honor of Rev. Adam Buddle, an English botanist. The specific epithet davidii honors the French missionary and explorer in China, Fr. Armand David who first reported the shrub to Europe.

Buddleia at times carries the nickname of "bombsite bush" which makes reference to the plant's ability to withstand tough environmental conditions. As an example, Buddleia has the ability to spring to life from heavily bombed communities in war-torn lands. Because of its resilience, it became a symbol of hope and rebirth to post-WWII Europeans.

Buddleia's vigor and resilience are not without controversy. After being introduced to the United States in the early 20th century, it gained the reputation of spreading quickly, especially in southern states. The good news is that the invasiveness of Buddleia varies by region. In colder climates, typically designated as zone 5 or lower, the harsh winter temperatures reduce the viability of its seeds, thus reducing the spread of the species in the wild. There are a few (southern) states that classify the species as a noxious species, although its use is not restricted in most states.

Additionally, breeding efforts have given rise to inter-specific hybrids of Buddleia that don't face the same restrictions as the species faces in some states. Hybrids that have demonstrated a two percent or lower seed viability can be planted in any state, including those that restrict the species. Therefore, anyone can responsibly welcome the beauty of Buddleia into their garden without the fear of it becoming invasive through the use of these hybrids.

Buddlia is a full-sun shrub that requires a minimum of eight hours of direct sun in order to thrive. Soil should be well-drained, since Buddleia is susceptible to root rot diseases that are characteristic of poorly drained, wet soil conditions. When establishing plants in poorly drained soil that cannot be corrected through the addition of organic matter, planting on a berm should be considered.

Considered fairly drought resistant, Buddleia suffers more when over-watered than under-watered. In average garden soil, Buddleia rarely needs to be fertilized. When fertilizer is called for, a balanced granular fertilizer applied (according to label recommendations) in spring is advised.

Because of its vigorous growth, Buddleia requires proper pruning, especially when located south of hardiness zone 5. It is notorious for producing "second story" flowers. This refers to the tendency of flowers to appear only at the top of the plant's leaf canopy. To encourage more eye-level flowers, consider pruning Buddleia just above new leaf buds in spring after new growth appears.

In colder climates, Buddleia normally freezes back to its crown each winter. In such cases, it is best to cut back all of the old wood to about 12 inches above ground in the spring. Doing so will result in more compact plants. They will quickly grow back to their normal height by fall and will flower just as prolifically in late summer since they bloom on new wood.

The follow represents a partial listing on newer, popular cultivars. While recent breeding efforts appear to be focused on the development of more compact plants, a few on the list are large and spectacular.

Baby Buzz Candy Pink: This new hybrid has a unique, cascading growth habit and can be used in containers or hanging baskets. Marketed as deer resistant it is listed as hardy to zone 5.

Butterfly Candy: The Candy series includes an array compact, well-branched and floriferous Buddleia and is available in multiple, vivid colors (Lil' Coconut, Lil' Grape, Lil' Lavender, Lil' Raspberry, and Lil' Taffy). They are ideal for small gardens or containers.

Butterfly Gold: This Buddleia boasts yellow to white and green variegated foliage which helps the plant to stand out even before it blooms. A bit tender, it is hardy to zone 6a and further south.

Cascade Collection: The Cascade collection of Buddleia from Walters Gardens are larger landscape plants with graceful, cascading flowers that make a lovely backdrop in garden designs. Grand Cascade boasts huge panicles (12-14 inches long and 4 inches thick) that cascade downward, similar to the look of weeping willow or bridal wreath spirea. Members of the series were trialed for four years with no observed seed set. The Cascade collection is considered hardy to zone 5.

Chrysalis series: This low seed set series is notable for its reliably compact growth with an excellent mounding habit. It can be used in hanging baskets, window boxes, or patio container combinations. It is hardy to zone 5a.

CranRazz and RoyalRazz: Both of these hybrids have excellent upright growth habit with impressive 8-in. panicles in dramatic, vibrant colors of cranberry red and bright purple. They are hardy to zone 5.

Flutterby Petite: Flutterby produces a compact plant with a mounding, spreading habit. The fuzzy, silvery green foliage accents its vibrant flowers which come in blue or pink. It is hardy to zones 5.

Gold Drop: A member of the HUMDINGER collection from Walters Gardens, Gold Drop has unique gold foliage making it a shrub that draws attention with or without flowers. It is considered hardy to zones 5.

Pugster Series: This series of Buddleia from Proven Winners grows only about two feet tall and equally wide. However, it has the large, full flowers normally seen on much larger cultivars. Available in blue, periwinkle, pink, and white, they bloom summer through frost with very colorful flowers. The Pugster® series offers vastly improved hardiness and winter survival over other types of dwarf Buddleia.

Sparkler Petite: This new compact beauty comes in both pink and purple flower colors. It exhibits a dense habit of growth to a height and width of between three and four feet, making it is perfect for small spaces. It is hardy to zone 5.

Acknowledgement: Information for this article was obtained from an article by the National Garden Bureau. Source: Dr. David Trinklein, MU Extension.

Dhruba Dhakal, PhD is a University of Missouri Extension Horticulturist, serving to Missourians about a decade in Central Missouri. Dhakal can be contacted at [email protected] with gardening questions.