Butterfly bush (Buddleia davidii) is a magnet for tiger swallowtails, monarchs, and other butterflies and moths. It’s a gorgeous deciduous shrub that usually grows about 2-3m tall. Semi-hardy to Zone 5 and hardy to Zone 9, it may die back to its base in harsh winters. However, if that happens, it usually sends out new growth in the spring. Its blossoms are similar to those produced by lilacs: long spike-shaped trusses of tiny flowers. Masses of the colourful, highly-fragrant, and pollen-rich flowers bloom from summer into fall.
Invasive Species
Butterfly bush is native to China. Known for its stunning, nectar-rich flowers and its ability to thrive in poor growing conditions, it was introduced as an ornamental plant around the world.
The very qualities that make butterfly bush a favourite also cause concern. It’s considered an invasive species in some areas and a noxious weed in others. In Washington State, USA, it’s illegal to buy or sell butterfly bushes (unless they are accepted sterile cultivars).
As the Invasive Species Council of BC points out, each of those gorgeous flower clusters on a butterfly bush can produce over 40,000 seeds. An entire bush can produce up to three million seeds in a single year. Seeds travel on the wind and in water and may remain dormant for years.
Once sprouted, a butterfly bush grows vigorously. It’s drought-tolerant and thrives in poor soil conditions–even growing in sidewalk cracks. It has spread quickly into established ecosystems and protected areas. It can crowd out native plants and alter soil nutrients. Regardless of growing conditions, butterfly bush can produce flowers and seeds in its first year, furthering its invasive cycle.
Sterile cultivars
Despite their issues, butterfly bushes remain extremely popular. A piece at ThoughtCo reveals that “the production and sale of butterfly bush was a $30.5 million industry [in the USA] in 2009.” Neither commercial growers nor home gardeners were keen to give up on the gorgeous plant.
Horticulturalists came to the rescue by developing cultivars that produce less than 2% of the seeds of traditional butterfly bushes. These cultivars are considered non-invasive and have been labelled as sterile. Even some municipalities that outright banned the sale of butterfly bush have amended their laws to allow for sterile cultivars.
Most of the sterile cultivars are hardy to Zones 5-9 and thrive in full sun. More details on select varieties are below:
Buddleia Lo & Behold® “Blue Chip”
This dwarf shrub grows to only about 45-75cm tall. It blooms with fragrant purple-blue flowers from summer until frost.
Buddleia Lo & Behold® “Purple Haze”
This particular cultivar is low (growing to a maximum height of 1m) and wide-spreading. It’s perfect for ground cover. Its fragrant purple flowers bloom from mid-summer to late fall.
Buddleia Lo & Behold® “Ice Chip”
This compact dwarf cultivar has fragrant white flowers that bloom continuously from mid-summer to mid-fall.
Buddleia “Asian Moon”
This tall cultivar can grow to between 1.5-2m in height. It produces stunning purple flowers with orange throats that bloom from summer until frost.
Buddleia “Miss Molly”
With a height of about 1.2-1.5m, this cultivar produces almost-red blossoms that are unique among butterfly bush varieties.
Buddleia “Miss Ruby”
Similar in height and appearance to “Miss Molly,” the Miss Ruby cultivar produces rich pink blossoms.
Not a True Host Plant
There is another issue with butterfly bush, though. While it provides abundant nectar for butterflies, it doesn’t support butterfly larvae or other types of wildlife. No caterpillars in North America will eat the leaves of butterfly bushes. Without caterpillars, there would be no butterflies. Butterfly bush is not truly a host plant since it doesn’t support butterflies through their entire reproduction and life cycle.
Create a Butterfly Host Garden
There’s nothing wrong with planting a butterfly bush just because you think it’s a beautiful plant. But if you’re truly interested in supporting butterfly populations, it’s better to create a host garden.
To give larvae something to munch on, establish companion plantings to your butterfly bush. Native plants that work well for this purpose include butterfly weed, milkweeds, joe-pye weed, and oak trees.
Another alternative is to skip butterfly bush altogether and plant a native alternative shrub instead. The Canadian-based Evergreen website suggests planting these native shrubs:
- Red flowering currant (Ribes sanquineum): This deciduous shrub grows up to 4m tall and produces pink draping blossoms that attract butterflies.
- Ninebark (Physocarpus capitatus): Produces white blossoms in the spring to attract butterflies. It can grow up to 4m high.
- Lilac (Syringa spp.): Lilac bushes are quite visually similar to butterfly bushes and also produce masses of fragrant blossoms. There are many different varieties and cultivars that flower at different times.
- Red Elderberry (Sambucus racemosa): This tall deciduous shrub can reach up to 6m in height. It produces white flowers in the spring that attract butterflies.
- Oceanspray (Holodiscus discolor): Another tall deciduous shrub that can grow to 4m in height. In the spring, it produces creamy white blossoms as plumes.
Butterfly bush is visually stunning, thrives in poor growing conditions, and produces ample nectar for butterflies. It sounds amazing but it’s not the best choice for a butterfly garden. Since it’s not native to North America, it didn’t evolve in tandem with our other plant and animal species. For that reason, it’s not a good host plant for wildlife, including butterfly larvae. Further, unless you choose a sterile cultivar, its invasive tendencies may cause issues in your region’s ecosystem. For all these reasons, it’s better to choose native plantings for your butterfly garden.