The Butterfly Bush

The Butterfly Bush

An Introduction to Buddleia davidii

By and Published January 08, 2010 Updated July 19, 2022

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Buddleia davidii (Butterfly Bush) is a wonderful shrub with large, fragrant, colorful flowers that attract a flutter of butterflies into your summer garden. Butterfly Bushes are extremely easy to grow and any novice gardener will have success with this genus. Plus they are the absolute best butterfly attracting plant you can grow. Buddleia breeders are hard at work creating marvelous new cultivars with novel flower colors, flower shapes, leaf colors, and dwarf habits. If you are still growing some of the older cultivars, you will be amazed how far they have come in recent years. 

 

We at Plant Delights Nursery and Juniper Level Botanic Garden grow many wonderful and rare butterfly bushes. We have 65 accessions of buddleias in the garden, and offer the finest and most unique cultivars for sale through our mail order nursery. We urge our readers to drop-by the garden during our open nursery and garden days to see our collection and check out our website to view our offerings. You can also read up on the top 25 plants for a butterfly garden here and learn how to design a butterfly garden here.

How to Grow Buddleia davidii

If you have seen our quick guide to caring for butterfly bush you know that Buddleia should be planted in full sun to ensure the best growth habit and the largest number of flowers. Most buddleia are tall and need to be placed at the back of a bed but there are some dwarf buddleia that will look good at the front of the border or as edging plants. Buddleia should be sited near a window, along a path, or close to a patio or porch where you can appreciate the scent the wonderfully fragrant blossoms during the summer months. In addition, they are quite tolerant of urban pollution which makes them well-suited to city landscapes and roadside plantings. 

Butterfly bushes are cold hardy to zone 5 which makes it suitable for most gardeners in the United States. However, hybrids that have been bred with other buddleia species may be less cold tolerant, as some of the other wild species are only hardy to zone 7 or 8. Near the edge of their hardiness range, they will die back to the ground in the winter and act more like herbaceous perennials. Buddleia are tough plants that can tolerate lean and alkaline soils. They look best in a well drained average garden soil with a pH of 5.5 to 7.0 but can tolerate an alkaline pH up to 8.5. Buddleia do not like poorly drained soils and will rot. Clay soils are best when amended with organic material or when the bed is raised up above the surrounding grade. Nor are they heavy feeders, so a good, nutritionally balanced soil with adequate organic amendments will suffice.

Buddleia davidii are drought tolerant and can be grown without much supplemental watering once established. During extended periods of dry weather they should receive a thorough watering once every couple of weeks. Container grown butterfly bushes will need more regular watering, typically once per day. Allowing a buddleia to become drought stressed will result in a much greater chance of insect infestations, such as spider mites.

Buddleia may be propagated by stem cuttings or by seed, with cuttings being the only option to reproduce named clones. Cuttings may be taken from softwood in May, half-hardened wood in July or from mature wood in October. Short, side shoots with many nodes work the best. Treat the cuttings with rooting hormone (1000-3000ppm IBA) and place them under mist. The tiny buddleia seeds should be collected from November to February when they are normally released. The seed require a short cold stratification period of only 4 weeks. They will germinate in 3-4 weeks if surface sown under light at 70°F to 80°F. Grow the seedlings until they have 2 or 3 leaves but take care to avoid damping off by providing air circulation and watering carefully. Harden off the seedlings by moving them outside after the last frost to a protected location and gradually increase the light level and moderate the temperature until they are growing in full sun at outside temperatures.

How to Prune a Butterfly Bush

Large buddleia hybrids will benefit from yearly pruning as they are weak-wooded and tend to split with age. Many of the commonly grown Buddleia davidii hybrids grow too large for the number of roots they produce. If they are not pruned annually, they will sometimes blow over in the wind. Also, most of the Buddleia davidii cultivars flower on new wood and therefore can be cut hard in late winter to stimulate flowering. We generally cut them back to 1'-2' tall, but many can be cut to the ground and will recover fine. Buddleia should not, however, be cut hard in the fall as the loss of insulating branches and stored sugars may reduce their winter hardiness. Wait for spring to prune your butterfly bushes. If seed production and dispersal is a concern on fertile buddleia, gardeners should remove the seed heads in October. The seed heads will not open up until November or December.

While hybrids need pruning, there is little need to prune species Buddleia, which are well adapted to their root system and will not fall over like the large hybrids. A few of the species, such as Buddleia alternifolia, actually flower on old wood and should only be pruned to maintain the shape and remove dead branches. Pruning on the species should be limited to minor shaping if needed. 

Butterfly Bush Pests and Diseases 

Buddleia are generally free of pests and diseases in the garden. When the plants are stressed they may be attacked by spider mites. Less frequently Japanese beetles, caterpillars, weevils, or mullein moth may feed on the plants. Scale has also been reported on stressed plants in some states. Spider mites can be controlled with a commercial miticide or oil spray, but it is better to keep the plant stress free by providing adequate moisture, soil drainage, and fertilizer. It is best to minimize chemicals, especially if your goal is to provide a breeding ground for butterflies.

Buddleia are considered to be deer resistant perennials. Deer prefer many other plants and will only feed on the butterfly bush as a last resort.

List of Butterfly species that are attracted to Buddleia flowers

The sweetly scented buddleia flowers attract butterflies and at times, the flowers will be covered with hundreds of them. Butterfly bush flowers serve as a nectar source for adult butterflies and the leaves too feed the larvae of some butterfly species. Buddleia are host plants to the North American butterfly species listed below: 

  • American Snout
  • Anise Swallowtail
  • Black Swallowtail
  • Cariable Checkerspot
  • Common Buckeye
  • Common Checkered-Skipper
  • Eastern Comma
  • Eastern Tiger Swallowtail
  • Echo Blue
  • Giant Swallowtail
  • Great Spangled Fritillary
  • Monarch
  • Mourning Cloak
  • Painted Lady
  • Peacock
  • Pearl Crescent
  • Pipevine Swallowtail
  • Polydamus Swallowtail
  • Red Admiral (prefer white blossoms)
  • Spicebush Swallowtail
  • Tortoiseshell
  • Two-tailed Tiger Swallowtail
  • Western Checkerspot
  • Western Tiger Swallowtail
  • Zebra Swallowtail

Bees, wasps, hornets, lady beetles, lacewings and moths also enjoy the flowers. Hummingbirds are attracted by the reddish cultivars. Other birds such as orioles and bushtits will feed on the nectar during the growing season and on the seeds in winter.

List of Buddleia Species

Today, there are dozens of buddleia cultivars on the market. Plant Delights Nursery is proud to have been the first to release two cultivars Buddleia 'Orange Scepter' (2009), and Buddleia davidii 'Potter's Purple' (1994). For more information on PDN releases, refer to our PDN Introductions.

Below is a short list of cultivars at Plant Delights Nursery and Juniper Level Botanic Garden. We strive to grow only the most interesting and evocative specimens, as well as some of the newest plants on the market.

Buddleia alternifolia (Alternate Leaf Butterfly Bush)

Buddleia alternifolia makes a 10-12' tall specimen with weeping branches, clothed in narrow leaves and adorned with long thin panicles of fragrant, light lavender flowers in early spring...very untypical. Do not cut this back in early spring or you will prevent it from blooming since it blooms on the previous seasons growth. This plant has an arching habit and looks great cascading over a wall. (Hardiness Zone 5-9)

Buddleia cordata var. tomentella (Hairy Mexican Butterfly Bush)

Tony Avent collected seed from this butterfly bush on the mountains between Saltillo and Monterrey, Mexico in 1994. In the years since, this has made a superb garden specimen to nearly 15' tall with an equal spread. The branches of grey-green leaves are topped with clusters of dirty white, but very fragrant flowers in fall and winter. (Hardiness Zone 7b-10, at least)

Buddleia davidii 'Adokeep' (Adonis Blue Butterfly Bush)

This selection is a member of the English Butterfly Series of Buddleia developed by Elizabeth Keep of East Malling, England. It makes a 5' tall well-branched specimen with small leaves and 10" long dark violet flowers. (Hardiness Zone 4-8)

Buddleia davidii 'Black Knight' (Black Knight Butterfly Bush)

This is the darkest-flowered of all the buddleias, almost a grape-violet, and always one of the most popular...awesome in front of gold-foliaged plants. The smaller foliage and shorter stature (50" tall), give Buddleia davidii 'Black Knight' the effect of being more graceful and airy. (Hardiness Zone 5-10) 

Buddleia davidii 'Bonnie' (Bonnie Butterfly Bush)

This Mike Dirr selection was named after his wife, Bonnie, and if you know Mike, you know that it must be one fine Buddleia! This giant deer resistant butterfly bush reaches 10' tall and is covered in large grey-green leaves, then topped from June until frost with large 10" panicles of very fragrant, light blue-violet (RHS 94D) flowers. (Hardiness Zone 5-10)

Buddleia davidii 'Cornwall Blue' (Cornwall Blue Butterfly Bush)

The flowers are very close to true blue and contrast very well with the fuzzy silver leaves. This plant grows to 8' tall. (Hardiness Zone 5-9)

Buddleia davidii 'Dartmoor' (Dartmoor Butterfly Bush)

Unlike most butterfly bushes, which end in a single panicle of flowers, Buddleia 'Dartmoor' performs like a good variety of broccoli and produces giant branched flower heads with additional flowering side shoots... but don't try to eat these! The medium purple flowers are wonderfully fragrant on this award-winning and large-growing 6' tall English hybrid. (Hardiness Zone 5-10)

Buddleia davidii 'Harlequin' (Harlequin Butterfly Bush)

Buddleia 'Harlequin' is a sport of Buddleia 'Royal Red' with creamy bordered leaves, providing a striking 7' tall accent in the garden. The reddish purple flowers top the plant throughout the summer. In the Southeast, it has unfortunately proven to be a weak grower and is very prone to having branches revert to green. (Hardiness Zone 5-10)

Buddleia davidii 'Potters Purple' (Potter's Purple Butterfly Bush) 

 

Buddleia 'Potters Purple' is our 1994 introduction, originating as a seedling found in 1984 by Jack Potter at the Wister Garden in Swarthmore, PA. We fell in love with this different color hue, almost a clear violet. Buddleia 'Potters Purple' is a very vigorous, 7' tall, upright deer-resistant grower with very long and fragrant flower panicles. At Mike Dirr's University of Georgia Buddleia trials, it has consistently ranked near the very top of 60+ trialed cultivars! (Hardiness Zone 5-9) 

Buddleia davidii 'Purple Prince' (Purple Prince Butterfly Bush)

This vigorous 6' tall oldie but goodie is topped with panicles of very fragrant violet blooms on a large 6' tall, upright plant (Hardiness Zone 5-10)

Buddleia davidii 'Royal Red' (Royal Red Butterfly Bush)

This 1928 hybrid from Good and Reese Nursery in Ohio is still one of the most sought-after of the butterfly bushes. Each 6-7' tall specimen is topped, from early summer through fall, with small panicles of delightfully fragrant, brilliant violet flowers (RHS 81A)...it's only red for color-blind butterflies and folks who write garden catalogs! (Hardiness Zone 5-9) 

Buddleia davidii 'Santana' PP12383 (Santana Butterfly Bush)

Released in 2007, this Rod Dransfield discovery is a sport of Buddleia 'Royal Red'. Buddleia 'Santana' is one of the most stunning buddleias that we've ever grown. Unfortunately, it's also one of the shortest lived. For some reason, this vigorous grower makes a nice 6' tall clump, and then inexplicably dies almost overnight. It's a real shame, because the variegated leaves that are green with a wide yellow margin are topped with reddish-purple then flowers that compliment the foliage. (Hardiness Zone 5-9)

Buddleia davidii 'White Bouquet' (White Bouquet Butterfly Bush)

This is one of the best white butterfly bush cultivars that we have found, with a nice dense growth habit to 6' tall, and absolutely smothered in rigidly upright fragrant white spikes all summer long. (Hardiness Zone 5-9)

Buddleia davidii v. nanhoensis 'Nanho Alba' (Nanho Alba Butterfly Bush)

This 6' tall introduction from the Boskoop Experiment Station in Holland has remarkably large bloom panicles of white, much longer than any of the other white butterfly bush cultivars that we have grown. (Hardiness Zone 5-10)

Buddleia davidii v. nanhoensis 'Nanho Blue' (Nanho Blue Butterfly Bush)

From the breeding program at the Boskoop Experiment Station in Holland comes a smaller leaved butterfly bush that still reaches 6' tall, contrary to some garden catalogs. The narrow silvery foliage is highlighted with the bluish flowers that are produced all summer. (Hardiness Zone 5-10)

Buddleia davidii v. nanhoensis 'Nanho Purple' (Nanho Purple Butterfly Bush)

From the Boskoop, Holland breeding program comes a lovely dark violet flowered form of the Nanho series of buddleias. The narrow leaves on a 6' tall plant serve as a nice light foil for the violet blooms all summer. (Hardiness Zone 5-10)

Buddleia fallowiana 'Alba' (Fallowiana Alba Butterfly Bush)

If you like butterfly bushes, then you are going to love this one! This is a white-flowering look-alike to Buddleia 'Lochinch' that we first received from Henry Ross of Gardenview. The foliage is felty grey, and the 4' tall clump is topped with delicious, long white flower panicles. (Hardiness Zone 5-9)

Buddleia lindleyana (Lindley's Butterfly Bush) 

This little-known Chinese species has shiny green leaves, cinnamon trunks, and graceful 2' long pendulous panicles of medium-lavender flowers that progressively open like a sparkler during the summer months. Our clone Buddleia lindleyana came from giant specimens in the Bolivia, NC garden of the late Francis Marion Galloway, where they have grown since the 1860s. We have limbed up our 7' tall specimen as a walk-underneath feature...a truly spectacular species which deserves much wider use. Its only bad habit is being stoloniferous, and that seems to slow slightly with age. (Hardiness Zone 5-9)

Buddleia loricata (Loricata Butterfly Bush)

This South African native species butterfly bush has a native distribution in Lesotho, Eastern Cape, KwaZulu-Natal and the Free State above 1800m. It has long, narrow, sage-like evergreen leaves and is a tidy round 4' tall shrub. The flowers are small cymes with a creamy white or yellow color and appear in June and July. This one flowers on old wood and if pruning is ever needed, it should be done in July when the flowering cycle has just finished. (Hardiness Zone 7b-9)

Buddleia marrubifolia 'Presidio' (Marrubium Leaf Butterfly Bush)

This is really cute, but completely unknown outside of its native Texas. In reality, you probably wouldn't recognize it if you saw it, as it looks more like a cross between a Buddleia and a lamb's ear. Buddleia marrubifolia makes a compact bush to 4' with small, round, felty, silver dollar-sized leaves. From late spring through the summer, the tips of each branch are home to marble-sized fuzzy orange balls... yes, these are the flowers. Buddleia marrubifolia is native to limestone slopes, so good drainage is essential. Our selection Buddleia 'Presidio' was made by the late Logan Calhoun of Texas for better hardiness. (Hardiness Zone 8-10)

Buddleia nivea var. yunnanensis (Snow White Butterfly Bush)

Buddleia nivea hails from southern China, where it makes huge, vigorous plants to 15' tall. The clumps are topped all summer with large terminal panicles of pale lavender. (Hardiness Zone 5-9)

List of Buddleia Hybrids

Buddleia 'Attraction' (Attraction Butterfly Bush)

This 55" tall buddleia is a seedling from UGA's guru of woody plants, Dr. Mike Dirr. The plant was eventually named by Ted Stephens of Nurseries Caroliniana. Buddleia 'Attraction' is toward the red-purple spectrum and a dramatic improvement over Buddleia 'Royal Red'. This is a tremendous breakthrough in butterfly bush breeding, and who knows?...perhaps it will attract redder butterflies. (Hardiness Zone 5-9)

Buddleia 'Blue Chip' PP 19,991 (Blue Chip Butterfly Bush, aka Buddleia 2004-09) 

This truly compact butterfly bush comes from the breeding program of Dr. Dennis Werner of the JC Raulston Arboretum at NCSU. Not only does this hybrid of Buddleia lindleyana, Buddleia 'Nanho Purple', and Buddleia 'Honeycomb' have very low seed set, but Buddleia 'Blue Chip' is one of the most compact Buddleias we have trialed and at the UK's Wisley trials was #2 in public voting after Dennis' Miss Ruby Butterfly Bush. The short internodes produce a compact plant that stays at 1-2' tall in the first season, and with an annual rejuvenation (beheading) it remains 2-3' tall. Unpruned plants will eventually reach 4' in height. Buddleia 'Blue Chip' is adorned throughout the summer with short spikes of lavender-blue...a perfect deer-resistant fit for small spaces and great for low-flying butterflies. (Hardiness Zone 5-9)

Buddleia 'Ellen's Blue' (Ellen's Blue Butterfly Bush)

What started as a stray seedling in the New York (Seneca Hills) garden of Ellen Hornig has now taken the gardening world by storm. Buddleia 'Ellen's Blue' makes a compact 4' tall deer resistant bush, smothered all summer in terminal spikes of blue-violet flowers (RHS 89D). This unique color in buddleias combined with the extraordinary fragrance, makes this one of the best new butterfly bush introductions...9 out of 10 butterflies choose Buddleia 'Ellen's Blue' ...we agree! (Hardiness Zone 5-9)

Buddleia 'Evil Ways' (Evil Ways Butterfly Bush)

This stunning Sean Hogan introduction is a bright yellow foliaged butterfly bush that originated at Sean's nursery as a seedling, probably from Buddleia 'Santana'. Buddleia 'Evil Ways' is highlighted throughout the summer with very dark purple terminal flower clusters. The color contrast of the flowers with the yellow foliage is simply superb. For us, Buddleia 'Evil Ways' has produced a 4' tall x 5' wide deer-resistant specimen, perfect for some really cool color combinations in the garden...yellow swallowtail butterflies are a nice touch. Without question, our favorite new butterfly bush in years! (Hardiness Zone 5-9)

Buddleia 'Lochinch' (Lochinch Butterfly Bush)

This hybrid of Buddleia fallowiana x Buddleia davidii has long been a garden favorite. Inheriting the silvery leaf backs from Buddleia fallowiana, this shorter cultivar (4-5' tall) makes a nice compact deer resistant clump with large foliage...the overall effect is a shimmering silver bush. From midsummer until early fall the plants are topped with fragrant, lavender-blue flowers...a great color echo for Russian sage. (Hardiness Zone 5-9)

Buddleia 'Miss Ruby' PP 19,950 (Miss Ruby Butterfly Bush)

Buddleia 'Miss Ruby' (Buddleia 'White Ball', x Buddleia 'Attraction'hybrid) is the second in a series of butterfly bushes from Dr. Dennis Werner of the JC Raulston Arboretum. Buddleia 'Miss Ruby', named in honor of JCRA benefactor Ruby McSwain, makes a compact 6' tall upright deer-resistant bush that only reaches 2-3' in year one, but is topped all summer with the brightest reddish-pink flowers ever produced on a Buddleia. In the 2008 trials at the UK's famed Wisley Gardens, Miss Ruby Butterfly Bush was the top public vote-getter from over 100 cultivars worldwide! (Hardiness Zone 5-9)

 Buddleia 'Orange Scepter' (Orange Sceptre Butterfly Bush) 

"And now for something completely different"...as the Monty Python troupe would say. This wild buddleia hybrid comes from the breeding program of Dr. Jon Lindstrom of the University of Arkansas. Jon combined the genetics of Buddleia stachyoides and Buddleia tubiflora to create an 8' tall deer-resistant butterfly bush that flowers virtually year-round in mild climates with a peak season of fall through spring. The 1' long terminal spikes of bright orange flowers, that open from bottom to top, could easily pass for leonotis. The trunks, which remain woody unless the temperature drops into single digits, are clothed with 11" long verbascum-like fuzzy green leaves...also great for sun rooms since it flowers all winter. (Hardiness Zone 7b-10)

Buddleia 'Pink Delight' (Pink Delight Butterfly Bush) 

This hybrid from The Netherlands' Boskoop Experimental Station is absolutely one of the finest pink flowered cultivars on the market. The silvery cast to the foliage (especially evident fall through spring) and compact (5' tall x 6' wide) habit combine to make this a truly spectacular deer resistant buddleia. Buddleia 'Pink Delight' is topped with large 1' long flower heads from June until frost. (Hardiness Zone 5-9)

Buddleia 'Summer Beauty' (Summer Beauty Butterfly Bush)

This exciting color breakthrough came from The Netherlands' Boskoop Experimental Station. This sister to Buddleia 'Pink Delight' has flowers that are more reddish-pink than any buddleias prior to the Miss Ruby Butterfly Bush. Combine the color with a smaller habit (to 48"), deer resistance, and silvery foliage...DY-NO-MITE! (Hardiness Zone 5-10)

Buddleia 'White Ball' (White Ball Butterfly Bush) 

This cute but quirky deer-resistant white butterfly bush, from the famed experiment station in Boskoop, Holland, is better-suited to the deer resistant or miniature train landscape than to the border. This rare genetic dwarf from a cross with Buddleia davidii v. nanhoensis, makes a tight ball, 3' tall x 3' wide, of greyish foliage topped all summer with miniature spikes of white flowers. Just wait until you see the miniature butterflies it attracts! Remember, it should only be pruned with miniature clippers and watered with tiny watering cans. (Hardiness Zone 5-9)

Buddleia x weyeriana 'Bicolor' (Bicolor Butterfly Bush) 

Buddleia 'Bicolor' is a 75" tall Mike Dirr introduction that arose as a seedling of virtually sterile Buddleia 'Honeycomb'. The flowers are an amazing lavender in bud, opening to peachy-pink with a yellow cast as they age. I've grown a lot of butterfly bushes and have seen nothing like this revolutionary new introduction. (Hardiness Zone 6-9) 

Buddleia x weyeriana 'Honeycomb' (Honeycomb Butterfly Bush)

From UGA's Dr. Mike Dirr comes this dazzling introduction that topped the comprehensive Buddleia trials held at the University of Georgia in the late 1990s. This 80" tall hybrid of Buddleia davidii and Buddleia globosa has produced a large butterfly bush that is best described as an improved Buddleia 'Sungold'. The 4-6" long flower panicles are a nice golden yellow and top the deer resistant plants.

Butterfly Bush History and Background

The common names for buddleia are butterfly bush and summer lilac although almost nobody uses the latter name. Butterfly bush should not be confused with the common perennial called butterfly weed, aka Asclepias tuberosa. 

The first species of buddleia known to science was a tropical shrub, the Central American native Buddleia americana which made its way to Europe from the Caribbean Islands in the 1730s. The buddleia that we commonly grow today, Buddleia davidii, was not discovered and brought into gardens until the 1890s.

The hundred or so wild butterfly bush species have a worldwide distribution between 40°N to 40°S latitude. Buddleia are divided into two groups, the new world buddleia, which are native from the southeastern United States to Chile, and the old world buddleia which are native to Africa and Asia.

The commonly grown Buddleia davidii is native from central China to Tibet at elevations up to 7800' (2600m) and is one of the most cold hardy buddleia species. There is a large species diversity of buddleia in Asia and the Americas, but the highest is in South Africa which leads scientists to speculate that they originally evolved there. Some species have a very wide natural range (Buddleia americana, Buddleia asiatica, Buddleia crispa) while others are rare and exist only in a small region (Buddleia coriacea, Buddleia utahensis). Most buddleia are woody shrubs from 6' to 16' in height. Others are 40-80' tall trees (e.g., Buddleia cordata Buddleia limitanea, Buddleia saligna), some are dwarf shrubs less than 3' tall (e.g., Buddleia pterocaulis, Buddleia utahensis), some are woody vines (e.g., Buddleia madagascariensis), and at the northern edge of their geographic range some are herbaceous perennials. Buddleia davidii is a widely grown ornamental plant in temperate areas around the world. Dozens of cultivars have been released covering a wide range of flower color, leaf color, and plant size. It is a very successful ornamental crop for landscape use, container gardening, and cut flowers. In the United States, buddleia are grown mainly in USDA hardiness zones 5-10, and are herbaceous perennials in the Zone 5 end of the range.

Outside of the garden, buddleia have only a few economic uses. Some cultures extract dyes or essential oils from the stems or the flowers. Others use extractions from the leaves to treat headaches, burns, wounds, or ulcers. Some species produce important secondary metabolites such as flavinoids, terpenoids, iridoids, or phenylethanoids that may have economic value.  

The native Chinese species, Buddleia davidii, has a reputation for being weedy in some places. Buddleia are pioneer successionary species: each plant produces millions of seeds and a plant can grow from seed to a mature flowering adult in a single year. The seeds have tiny wings on them and can float a long distance in the wind. Buddleia davidii plants will colonize any piece of bare soil in sunny locations such as roadsides, riparian areas, pastures, and other disturbed areas. After World War II, many of England's bombed-out home sites had Buddleia growing on them. Even today, the English countryside is painted with butterfly flowers every summer. Buddleia do not like direct competition from trees or other tall plants, and therefore will die out in an area with a climax forest successionary regime.

Buddleia davidii is considered to be an invasive weed in New Zealand, England, France, and the US (Oregon and Washington state). Australia, Fiji, and Hawaii consider it to be potentially invasive and maintain a careful watch. Buddleia davidii has naturalized in England, as well as many US states such as California, Pennsylvania, North Carolina, Virginia, Delaware, Maryland, New Jersey, Kentucky, and West Virginia but is not considered invasive or harmful.

For gardeners whose property borders a non-forested natural area, use the sterile or low fertility cultivars or remove the seed heads in the fall before they open. Many of the modern cultivars of Buddleia davidii have dramatically reduced fertility and are not invasive. Some hybrid cultivars (such as Buddleia 'Blue Chip') are almost completely sterile and pose no threat. Some low viability selections include Buddleia weyeriana, Buddleia fallowiana, Buddleia hemsleyana, Buddleia longifolia, Buddleia macrostachya, and Buddleia nivea.

Buddleia Butterfly Bush Traits (Shape, Flower Colors, etc.)

Buddleia leaves are lance-shaped (lanceolate) and are arranged oppositely along the branch (except Buddleia alternifolia). The leaves range in size from 1/2" to 11" long (1 to 30cm). Some species are deciduous, some are semi-evergreen, and some are evergreen. The common Buddleia davidii is semi-deciduous in North Carolina. Many butterfly bush leaves have small white hairs on their surface and some cultivars such as Buddleia marrubifolia are hirsute enough to give the leaf an attractive silvery-grey appearance. The hairy cultivars are also more resistant to spider mites and the hairs also reduce water loss which make the plants more drought tolerant. 

Buddleia "flowers" are actually inflorescences; a collection of many small "florets" on a single floral structure. Each inflorescence consists of dozens of small tubular florets that are 0.5" long and 0.1" wide (1cm by 3mm) each with 4 spreading petals.

The fruit is usually a two-valved capsule that splits at maturity to release about 50 seeds. Some species (e.g., Buddleia axillaris, Buddleia japonica) produce berries instead of capsules. The seeds are generally not released until late December and they release gradually over several months.

Most common garden varieties of buddleia are old world species and the inflorescence is a cone-shaped panicle. However, new world buddleia species tend to have spherical inflorescences called globose cymes or racemes. The inflorescences may occur at the tips of the stems, or along the length of the stem. In some species, the inflorescences span dozens of nodes on the stem and have small bracts or leaves between them. Buddleia panicles are from 4" to 20" long (10 to 50cm) and cymes may be from 2"-5" across depending on species.

Buddleia davidii, Buddleia fallowiana, Buddleia officinalis, Buddleia paniculata and Buddleia salviifolia have erect panicles at the tips of the branches. Buddleia asiatica, Buddleia colvilei, and Buddleia lindleyana have panicles that are long enough to arch over or cascade downward from the branches. The cymes and racemes of new world species may form at every node on a long cascading branch (Buddleia alternifolia) or an erect branch (Buddleia globosa, Buddleia utahensis). Cymes and racemes of new world species may also form at the tip of a branch (Buddleia crispa, Buddleia saligna).

Flower color may be white, purple, blue, pink, yellow, orange, or a reddish-purple color that buddleia marketers like to call "red". Buddleia davidii and most of the other old world species have separate male and female florets on the same plant (monoecious). New world species tend to have separate male and female plants (dioecious). There are also perfect-flowered species (hermaphrodites). Plants are self-fertile and members of the genus easily cross with each other to form interspecific hybrids with intermediate floral traits.

Common garden butterfly bushes (Buddleia davidii, Buddleia lindleyana, Buddleia fallowiana) have flowers with a sweet honey fragrance that is strongest at midday. The agreeable scent attracts a variety of butterflies, insects, birds and of course, gardeners. A few wild species have little scent, or a fetidly sweet scent that some people find disagreeable. Buddleia salviifolia is said to have the best fragrance of all, smelling like Chanel perfume. 

The common garden species are long-day plants and flower in the summer. Flowering starts in July and lasts until first frost, but most of the buddleia hybrids produce their best floral show in early summer. In hot summer climates with warm nights, the summer produced inflorescences will often be dramatically smaller, returning to their full size only when fall approaches and the night temperatures cool.

Some of the other buddleia species are short-day plants such as Buddleia alternifolia which blooms in early spring. Both Buddleia asiatica and Buddleia officinalis bloom in late winter. Interestingly, the natural diploid species are usually short-day plants and the natural tetraploid species are usually long day plants.

Buddleia Taxonomy - How the Butterfly Bush Got It's Name

An alternate spelling for buddleia is "buddleja", and like a good mystery novel, the nomenclatural plot thickens. Reportedly, British surgeon and botanist Dr. William Houstoun (1695-1733), in his Catalogus plantarum Horti regii parisiensis, first spelled the name "buddleia". Carl Linnaeus then reportedly misspelled it in the taxonomic bible, Species Plantarum as both "buddleja" in the text and "budleja" in the index. In a later edition of Houstoun's work, published by Sir Joseph Banks in 1781, three different spellings can be found: buddleja, buddleia, and buddlea. Many taxonomists also consider the name buddleja to have been misspelled, because according to the rules of Latin; the suffix "ja" is grammatically incorrect and the suffix "ia" is the proper way to create a genus from the name buddle. Nowadays, most European taxonomists use the spelling buddleja, but almost everyone else uses the orthographical variant spelling buddleia...and we will follow the latter convention in this essay. In recent years major references from the American Horticultural Society, and the Royal Horticultural Society have been reverting from buddleia to buddleja. Many American horticulturalists rely on a reference book called Hortus Third which uses the term buddleia.

The name buddleia commemorates the amateur botanist and bryophyte expert, Reverend Adam Buddle (1662-1715). Buddleia was named for Buddle posthumously to recognize him for writing an early Flora of the British Islands. Oddly enough, Reverend Buddle never grew a butterfly bush. The first known butterfly bush species, Buddleia americana, wasn't sent to European botanists until 1730, after Buddle's death. The commonly grown Buddleia davidii, was named for French Jesuit missionary and naturalist, Pére Armand David, who first discovered it.

The genus Buddleia has been tossed about between taxonomic families. Buddleia was originally assigned to the family Scrophulariaceae by taxonomist Antoine Laurent de Jussieu in 1789, but in 1856 Taxonomist George Bentham moved it to the family Loganiaceae. In 1975 it was moved to its own family, Buddlejaceae, where it has stayed until very recently. Recent DNA analysis and phylogenetic studies have generated cladograms that place the entire family Buddlejaceae inside of the family Scrophulariaceae. The family Scrophulariaceae is complex and is considered to be a catch-all family for undefined genera in order Lamiales. However, this story is not over yet, work is still ongoing to sort it all out. 

The genus Buddleia has over 100 species in it, but only a handful are used in ornamental gardens. These include Buddleia alternifolia , Buddleia asiatica, Buddleia colvilei, Buddleia crispa, Buddleia fallowiana, Buddleia globosa, Buddleia lindleyana, Buddleia marrubifolia, Buddleia officinalis, Buddleia paniculata, Buddleia saligna, Buddleia salviifolia, and the ubiquitous Buddleia davidii from which most of the common garden cultivars arise. A hybrid of the otherwise unused species, Buddleia stachyoides and Buddleia tubiflora also has garden merit. The man made interspecific hybrid Buddleia globosa x Buddleia davidii has been given the unique epithet Buddleia x weyeriana. This cross was originally made by the first buddleia breeder, Mr. Van de Weyer in Dorset, England in the early 20th century.

Butterfly Bush Genetics & Breeding

Modern breeding of buddleia began in 1900. Naturalist E.H. Wilson made germplasm collections of Buddleia davidii from western China while traveling for the Veitch Nursery in London and the Arnold Arboretum. The material sent to this plant nursery formed the basis of the modern garden hybrids. The Buddleia x weyeriana created in 1914 by Mr. Van de Weyer is still popular today. 

Currently new cultivars are being announced every year by breeders and plant nurseries. The new cultivars offer novel combinations of plant height, leaf color, and flower color. Flower colors vary along a continuum and include hues of white, blue, purple, pink, orange, and yellow. A few cultivars even have flowers with branched panicles. Newer cultivars tend to be sterile or have vastly reduced seed germination and are thus less likely to seed around. Since sterile hybrids do not expend energy producing seed, they are usually very floriferous. Garden cultivars exist at every possible plant height from 2' to 15' and breeders are focused on releasing dwarf selections or more tightly branched selections that can fit into smaller gardens. Other breeders focus on leaf characteristics such as leaf color, variegation, and hirsuteness.

Buddleia breeders sometimes select plants for polyploidy (more than 2 sets of chromosomes) because some polyploids are sterile. Up to 40% of the buddleia species are natural polyploids. Buddleia have a chromosome number of n=19 (that is, there are 19 chromosomes in each set). There are also buddleia that are natural tetraploids (4n)(e.g., Buddleia davidii). Triploid buddleia also exist and are sterile. Asian species tend to be polyploid and new world species tend to be diploid. It is hypothesized that buddleia are allopolyploids that arose from a intergeneric cross between Gomphostigma (2n=14) with Retzia or Nuxia (2n=24).

The most prominent modern Buddleia breeders and programs are:

Dr. Dennis Werner of North Carolina State University has a decade long buddleia breeding program that focuses on novel leaf color, novel flower color, and dwarf habit. Werner makes controlled crosses using Buddleia davidii, Buddleia globosa, Buddleia lindleyana, Buddleia davidii var. nanhoensis, and Buddleia fallowiana. He is currently screening for sterility, true red flower color, and better yellows and oranges. His two recent releases, Buddleia 'Blue Chip' and Buddleia 'Miss Ruby' have won many accolades. In particular, Buddleia 'Blue Chip' is a breakthrough in breeding for its extremely dwarf habit. As it is nearly sterile it does not pose any "flight risk" like older cultivars. He is using Buddleia 'Blue Chip' and another dwarf, Buddleia 'White Ball' as parents for new hybrids. He has buddleias in the pipeline that are even smaller than ‘Blue Chip’ and that are seedless. Dr. Werner has also directed graduate students in the study of genetic mechanisms of flowering in buddleia and is experimenting with using radiation to induce mutations. This research may someday help create better flowering cultivars. In the future, look for new exciting cultivars to come out of this breeding program including a dwarf white, a dwarf lavender, and a semi-dwarf with semi-pendant inflorescences. 

The late Dr. Jon Lindstrom of the University of Arkansas had a two decade long buddleia breeding program with a three-pronged approach. One goal was to release sterile hybrids that produced little or no seed. A second goal was to create silvery foliaged plants (like Buddleia 'Lochinch') with a wide range of flower colors. His third goal was to use uncommon buddleia species that bring novel traits into garden cultivars.

There are a number of new cultivars entering the market from breeder Peter Podaras, currently at Cornell University. Peter has created some dwarf cultivars and has used some lesser known buddleia species in his crosses. His first plants entered the market in 2010.

Dr. Mike Dirr [retired] of the University of Georgia ran a buddleia evaluation program that focused on attractive garden hybrids and spider mite resistance. His program released the popular hybrid cultivar Buddleia 'Honeycomb' which is considered to be the best yellow-flowered cultivar. He also released the unique Buddleia 'Bicolor' with its two-toned flowers.

The Boskoop Agricultural Research Station in the Netherlands selected and released several excellent cultivars including the compact Buddleia 'White Ball' and Buddleia 'Pink Delight'. Elizabeth Keep of East Malling Research Station in Kent England has bred many cultivars of buddleia with the goal of refining the habit to make bushier plants that are smaller in stature.

These folks should be commended for their wonderful work. Plant Delights Nursery is happy to offer some of their best cultivars for sale and Juniper Level Botanic Garden displays many of these fine selections.

Conclusion

Buddleia are admirable garden shrubs for any garden from Zone 5 south. Buddleia are beautifully floriferous and sweetly odiferous and will attract thousands of butterflies to your garden. You may be asking yourself, "What is the best butterfly bush for my garden?" If you want incredible yellow foliage, try Buddleia 'Evil Ways'. For nearly red flowers, choose Buddleia 'Miss Ruby'. If you are looking for rare, eye-popping, yellow or orange flowers, you'll want Buddleia 'Honeycomb' or Buddleia 'Orange Scepter'. For a demure look, try the pastel colored Buddleia 'Pink Delight'. Buddleia 'Blue Chip' and Buddleia 'Ellen's Blue' are great compact blue-flowering buddleias. For the smaller garden, Buddleia 'White Ball' is a great white butterfly bush with a tidy compact habit. If you want to impress your gardening friends, try the truly unusual Buddleia 'Bicolor' or Buddleia lindleyana. Whichever one you choose, you will be sure to get a winner!

References
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