7 Reasons You Shouldn’t Plant Butterfly Bush
The beauty of buddleia is alluring for gardeners who love flowers and butterflies, but this invasive bush may actually have a negative impact on your garden and the surrounding ecology. Garden expert Logan Hailey explains why.
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With its long trusses of dazzling purple blooms, butterfly bush, or Buddleia, is one of the most popular ornamental shrubs. These elegant arching shrubs have abundant lilac-like flowers that blossom all summer long, attracting thousands of bees and butterflies. But, in spite of its aesthetics, there are many reasons why you shouldn’t plant this shrub.
Unfortunately, the beautiful butterfly bush is a hidden beast in most areas of the United States. This invasive bush can actually negatively impact your garden and the surrounding ecosystem.
Why Shouldn’t You Plant Butterfly Bush?
Butterfly bush (Buddleja davidii) is considered invasive in most of the United States. The plant can escape cultivation and displace native species, causing ecological disruption. These flowering shrubs spread rapidly, choking out native plants and altering the food and habitat resources for local wildlife, including butterflies, bees, and birds. Ironically, the invasive bush can harm butterfly life cycles because it overgrows the native flowers that butterflies rely on to reproduce.
A single flower can produce over 40,000 lightweight seeds that spread via wind, water, and animals to quickly colonize nearby areas. This noxious weed also has an extensive root system that can cause cracks and structural damage in masonry and walls. Moreover, the flowers are highly attractive to mosquitoes, which can be a major nuisance and health issue in the garden.
7 Negative Impacts of Buddleia
Buddleia plants are incredibly attractive, but an ugly personality ruins a pretty face. Unfortunately, the negative impacts of this shrub overshadow its beauty. Here are 7 reasons why you shouldn’t plant butterfly bush, and what to grow instead.
It’s an Invasive Plant
Buddleja davidii is native to China. It grows wild in dense thickets on mountain slopes, stream banks, and forest clearings, thriving in rocky, poor soil. The plant can grow up to 12 feet tall and spread 4-15 feet wide. It is persistent through cold winter temperatures and spreads rapidly in many climates, often escaping cultivation.
Butterfly bush is highly invasive in the Pacific Northwest, including Washington and Oregon, where it is considered a noxious weed. It has naturalized throughout the Eastern U.S. and is notably aggressive in Pennsylvania, West Virginia, New Jersey, North Carolina, and Kentucky.
Plant Alternative:
If you absolutely must have a butterfly bush, be very careful to select a non-invasive cultivar. Plant breeders have worked to develop sterile, non-invasive varieties. Legally, these plants must have less than a 2% germination rate to qualify for sale in Oregon and Washington. Often, they will hybridize two Buddleia species to yield a shrub that produces inviable pollen so it cannot cross with other butterfly bush plants. To distinguish these plants from the true, invasive species, officials require them to be labeled as “summer lilacs.”
Non-invasive summer lilac varieties include:
- Buddleia Lo & Behold® ‘Blue Chip Jr.’
- Buddleia Lo & Behold® ‘Blue Chip’
- Buddleia Lo & Behold® ‘Pink Micro Chip’
- Buddleia ‘Miss Molly’
- Buddleia ‘Miss Violet’
Take special care to double-check the labels of your desired plant cultivar. Also, note that whether or not a cultivar can be truly sterile has been a topic of controversy among restoration ecologists.
Disruption of Local Ecosystems
The invasive nature of butterfly bush makes it disruptive to local ecosystems. It is highly likely that this bush will “escape” your yard, spreading to neighboring parks, ditches, or wild areas. The highly vigorous shrub can quickly choke out native plants, creating a monoculture of the noxious weed. As it takes over, it reduces the biodiversity of an area and kills native plant species that local fauna rely on to survive. The tall shrubs can shade out lower-growing plants and suck up nutrients in the soil.
This ecological disruption poses particular problems for native wildlife like bees, insects, and birds. The plant produces copious amounts of nectar, which may seem like a positive benefit for pollinators, but it can also disrupt their migration and reproductive patterns. The nectar only benefits them at one stage during their lifecycle.
As we’ll explain below, butterfly bush flowers become especially harmful and drug-like for butterflies. They may slurp down its nectar, but the shrub aggressively overgrows the native host plants that butterfly species need to lay their eggs on. Caterpillars are specifically adapted to certain host plants that they munch on before they go into their cocoons and emerge as adult butterflies to repeat the cycle. These larvae cannot eat the plant’s leaves, and the shrubs don’t provide the right conditions for egg-laying. In areas where butterfly bush proliferates, the caterpillar host plants are often choked out of their native habitat, leaving nowhere for butterflies to lay their eggs.
Plant Alternative:
Lead Plant (Amorpha canescens) is a rounded native shrub with grayish-green foliage that adds a feathery appearance to the landscape. The spikes of slender purplish-blue flowers bloom from late spring to early summer and provide vital nectar to native pollinators. Lead Plant grows wild throughout the High Plains of North America, from southern Canada to Texas. The plant dies back in the winter, but remains perennial in zones 2-9. At just two to three feet tall and wide, it is much stouter than a butterfly bush and easier to control.
Lead Plant is the host plant for many butterfly and moth species, including the Magdalen Underwing, Southern Dogface Sulfur, Eastern-Tailed Blue, and Silver Spotted Skipper butterflies. These species can savor the nectar of Lead Plant during their adult phase, and munch on the leaves of the bush during their larval (caterpillar) phase.
Aggressive Spread
A single inflorescence can produce over 40,000 seeds. Many plants produce dozens to hundreds of these panicle flower clusters throughout the summer season. These seeds are lightweight and shaped with little wings that help them easily disperse far and wide. When rain or wind blows through a dried seed head of Buddleia, the capsules burst open and spread the seeds over vast areas. These fast-maturing plants only need one season of growth to produce mature seeds, meaning that populations can quickly get out of hand.
A secondary problem is this shrub’s winter hardiness. It remains an evergreen perennial in zone 7 and warmer. In zones 5 and 6, plants typically die to the ground but come back with a vengeance in the spring. This may seem like a wonderful benefit for your ornamental garden, but it can be very harmful to wildland ecosystems where butterfly bushes are taking over the beautiful diversity of native herbs and shrubs that have evolved there for thousands of years.
Fortunately, they do not typically spread vegetatively by roots or runners. Still, they can overgrow an area in a very short amount of time. The plants are particularly adept at invading sunny, dry sites with well-drained, disturbed soils. They tolerate clay, but cannot take over in poorly drained conditions. The shrubs also struggle in shady areas without full sun.
Plant Alternative:
Bottlebrush Buckeye (Aesculus parviflora) is a gorgeous shade-tolerant shrub with big white panicles of flowers. The plant averages 8-12 feet tall and 8-15 feet wide, with a similar stature to butterfly bush. This widely adaptive native species blooms throughout early and mid-summer, delighting butterflies and hummingbirds. In the autumn, the foliage turns bronze, yellow, and orange.
The shrubs produce intriguing pear-shaped nuts (nicknamed “buckeyes”) that are glossy and attractive, but inedible. Bottlebrush Buckeye is low-maintenance and grows in average soils as long as there is moderate moisture. This Southeastern native grows naturally in woodland areas throughout Alabama, Georgia, and Florida, but is safe to plant anywhere in the U.S. between hardiness zones 5 and 9.
Roots Can Destabilize Masonry and Walls
You might have heard that it’s a bad idea to plant fast-growing trees like maples and locusts near your home because they can damage the foundation. Butterfly bush poses similar problems, but it is most infamous for its ability to damage walls. Buddleia roots are very aggressive and easily grow through cracks in masonry and bricks.
As the roots spread, they destabilize structures, potentially making them unsightly, dangerous, and susceptible to collapse. Buddleia root systems weaken the building materials of any structure they grow near. While gardeners may innocently plant the shrub for its beautiful flowers, they may face a not-so-pretty repair bill years down the line. The costly repairs and potential permanent structural damage are just not worth the risk.
Plant Alternative:
Ceanothus thyrsiflorus, or Blue Blossom, is a wild California lilac native to the West Coast, including most of California and Oregon. This large evergreen shrub has a gorgeous upright stature with arching branches similar to butterfly bush, but without the invasive risks. The flowers bloom in big fluffy clusters up to eight inches long, jam-packed with hues of blue blossoms. The yellow stamens stick out from the centers of the little flowers, adding unique color.
This native shrub thrives in areas with full sun and good drainage. They appreciate some afternoon shade. The foliage of Blue Blossom is lustrous green and oval. It grows quickly in its native range of coastal chaparral and open, wooded slopes. The flowers are magnets for bees, butterflies, moths, and other pollinators. Birds enjoy the seed pods.
This Ceanothus is recommended for wall-side borders because it makes a beautiful hedge and doesn’t pose risks to infrastructure. It is highly unlikely that the roots will break through masonry or foundation. These shrubs have shallow root systems that only spread about the distance of the canopy. The roots are unlikely to dig deeper into the soil or break through cracks.
Mosquitoes are Attracted to the Flowers
Bees and butterflies aren’t the only ones who love this bush! Pesky mosquitoes are actually magnetized to the flowers, making this shrub extremely undesirable for backyard landscapes where you want to hang out for summer barbeques or evening tea. Mosquitoes don’t only like blood; they are also hungry for a sweet treat to fuel their early and late stages of life.
Research shows that mosquitoes are more likely to lay their eggs in water sources near flowering butterfly bushes. After a mosquito feasts on the blood of animals and humans, the females are impregnated and go seeking floral nectar to feed themselves and the next generation. If there is a puddle, pond, stream, or fountain near the butterfly bush, they will eagerly lay their eggs nearby so the next generation can feast on the sugar right after emergence.
Plant Alternative:
Instead of attracting mosquitoes to your yard, you can deter them with Catnip (Nepeta cataria). Although this perennial herb is smaller than butterfly bush, it provides an equal amount of elegant beauty and floral display. The mint-family shrub has a strong odor that cats love and mosquitoes despise. Catnip is especially popular as a companion plant in vegetable gardens because its thyme or mint-like fragrance deters many different insects.
Researchers even found that the essential oil in catnip (nepetalactone) is nearly ten times more effective at repelling mosquitoes than DEET! While you may need a concentrated version of catnip’s oils to achieve these results, it is still worth having in the garden. Catnip is extremely hardy and easy to care for, plus the plant flower for nearly two months. The spike-like racemes are loaded with pink and purple blossoms that butterflies and bees adore. If you shear the plant after the first bloom, it will eagerly produce another cycle of flowers.
Buddleia is Banned in Many States
In addition to all the environmental and logical reasons why you shouldn’t plant butterfly bush, it may also be illegal in your area. Washington and Oregon both list the plant as a noxious weed and prohibit its sale within state lines. The Oregon Department of Agriculture lists a few approved cultivars that produce nearly sterile seeds. Legally, these cultivars can only have two percent or less of their seeds viable.
While you may not face extreme legal consequences by planting this invasive species, it is best to avoid exacerbating the problem in the Pacific Northwest. Conservationists and officials promote removing butterfly bushes and trashing or burning all plant material to prevent spread.
Ironically, It Can Harm Butterflies
If you love butterflies and long to grow a mystical butterfly garden, this shrub may not be the best for you. Butterfly bush can, ironically, harm its namesake insects. It may seem like the colorful nectar-loaded flowers benefit butterflies, but they actually cause more harm than good. Adult butterflies flock to Buddleia blossoms, but when it comes time to lay eggs and produce the next generation, the shrub becomes problematic.
Buddleia is native to China, which means all of its native pollinators also reside there. North American butterflies have adapted for thousands of years to reproduce in symbiosis with specific North American native plants, called host plants. When our butterflies gorge themselves on the nectar of a foreign plant, they become distracted from the host plants that they need to feed on to produce the next generation.
You’re probably familiar with the metamorphosis crucial to butterfly life cycles. Butterfly bush only supports butterflies during one stage of the life cycle— the adult stage. Larval caterpillars cannot eat Buddleja foliage, and the shrub cannot support butterfly eggs. Whether you love monarchs or adore native swallowtails, no native North American butterflies can use butterfly bush as a host plant.
Plant Alternative:
Native milkweeds (Asclepias spp.) are the best possible garden option for butterfly lovers. Milkweed plants are vital host plants for Monarchs, Grey Hairstreaks, and many other species of butterflies. The abundant clusters of flowers are gorgeous and colorful, providing important nectar for migrating butterflies. When the butterflies are ready to lay their eggs, milkweed also serves as a host plant and “nursery” for newly hatched caterpillars that munch on the leaves.
Milkweed wildflowers are very easy-to-grow perennial bushes with flat-topped clusters of bright orange, yellow, pink, or purple flowers. The attractive dark green leaves are long and pointed, and highly edible for caterpillars. The plants bloom all summer long and easily self-sow without becoming invasive in the garden.
Milkweeds are superbly drought tolerant, unlike butterfly bush, which is quite water-demanding. The plants can grow in nearly any soil and are adapted to many regions of the United States. Milkweed is the perfect addition to a meadow garden, pollinator planting, or perennial border. The long floral stems make beautiful cut flowers for arrangements.
You can use the Xerces Society Milkweed Finder to find milkweed species that are native to your area. Avoid planting the non-native tropical milkweed (Asclepias curassavica) because it can harm Monarchs by disrupting their migration patterns.
Final Thoughts
Ultimately, you can plant whatever you want in your garden, but your decisions may have a lasting impact on local ecology. If you love butterflies and care about preserving native plant species, steer clear of butterfly bush. This invasive shrub rapidly outcompetes local species, aggressively spreading through wildlands and disturbed areas.
Its strong roots can cause major structural issues with walls and foundations. Moreover, the nectar-rich flowers can actually harm butterfly species by providing excessive floral resources for adults without offering the important nesting and hatching sites for caterpillars of the next generation.
If you absolutely adore the appearance of butterfly bush, search the Oregon Department of Agriculture list of approved cultivars that produce sterile, non-invasive seeds.
