Butterfly bush (Buddleja davidii – often spelled Buddleia) is a favorite shrub of many gardeners because of its colorful flowers and ability to attract a variety of beneficial insects. As the name implies, the shrub is particularly attractive to butterflies. Native to China, it is adapted to all regions of South Carolina; however, it may be killed to the ground during harsh winters. In some areas of the US, it is considered weedy, and its planting is discouraged. This does not seem to be as much of an issue in the southeast with the exception of B. Lindleyana which suckers prolifically. Weedy seedlings should be dug-out where unwanted.
This deciduous to semi-evergreen shrub typically grows from 6 to 10 feet tall by 4 to 10 feet wide with a rather open, arching form. Their stems are square in cross-section, and young shoots are covered by dense, white hairs. Leaves are opposite, 3 to 5 inches long by 1 to 3 inches wide, varying from deep green to gray-green to silvery-gray. The leaves of some cultivars are densely hairy underneath. Size, form and leaf color can vary widely by cultivar and should be considered when purchasing plants.
Butterfly bushes grow very fast and can reach mature size in 1 to 2 growing seasons.
Butterfly bushes form the foundation for numerous butterfly gardens and are prized for their long, summer bloom period. Many cultivars will flower from June through October (if deadheaded) with peak bloom in July and August. They produce 5- to 12-inch-long panicles (i.e. long, slender flower clusters) in white, blue, lavender, pink, purple, yellow and many intermediate shades. The flowers are a nearly irresistible nectar source for butterflies, bees, lady beetles, and other pollinating insects as well as the occasional hummingbird. Additionally, their flowers have a pleasant fragrance. The shrubs are essentially round in outline and form an excellent backdrop for perennial borders. Removing old flowers will encourage new blooms.
Butterfly bushes are amazingly tough plants and grow well under a variety of conditions. The one critical requirement is well-drained soil as their roots will quickly rot when waterlogged. Full sun is needed to ensure adequate flowering, and they prefer a soil pH of 6.0 to 7.0. Like most shrubs, they benefit from a 2- to 3-inch layer of organic mulch. Once established they are fairly drought tolerant and only require moderate fertilization.
These shrubs are very cold-hardy (USDA Zones 5 – 9), but as mentioned earlier, they may be killed to the ground by very low temperatures. This is not a problem since they will re-sprout vigorously from the crown (i.e. where the stems meet the roots). In fact, pruning butterfly bushes to within one foot of the ground annually enhances the flower display. This should be done before new growth begins in the spring since they flower on new growth. Avoid fall or winter pruning which increases the risk of cold damage.
Seeds form after flowering and the dark seed heads are generally considered unattractive. Deadheading the spent panicles before they go to seed provides a neater look to the plant, lengthens the bloom period, and prevents unwanted seedlings in the garden.
Butterfly bushes are relatively trouble free when the proper conditions are provided. However, spider mites can be a problem when the plants are drought stressed. Nematodes are also a problem, particularly in the sandy soils of the coastal plain. Downy mildew, caused by the fungus Peronospora hariotii, may occur during cooler temperatures with extended leaf wetness on Buddleja x Weyeriana cultivars. Pesticide use on these shrubs is discouraged, particularly when in bloom, because of the wide variety of beneficial insects present at that time. Some people with sensitive skin may be irritated by the foliage.
There are an overwhelming number of cultivars available and also a number of related species and hybrids. The list below contains some of the most commonly available cultivars. It is advisable to buy from reputable nurseries as plants of his species are often mislabeled.
Large Cultivars (greater than 6 feet tall):
- ‘Attraction’ has magenta, nearly red flowers with attractive foliage.
- ‘Bicolor’ (B. x Weyeriana) has lavender flower buds that open to a peachy-pink with a yellow cast as they age.
- ‘Black Night’ is the most commonly available cultivar, and has dark purple flowers. The darkest butterfly bush flowers available.
- ‘Dartmoor’ has mauve-to lilac-colored flowers borne on large, branched flower heads.
- ‘Guinevere’ has vibrant purple-black, fragrant flowers and dark blue-green foliage.
- ‘Honeycomb’ (B. x Weyeriana) has fragrant, golden yellow flowers with attractive green foliage.
- ‘Lochinch’ has sweet scented, light lavender-violet flowers and felted foliage with a silvery cast. ‘Lochinch’ is a hybrid between B. davidii and B. fallowiana.
- ‘Pink Delight’ flowers are a true pink on large panicles. The foliage has a silvery cast.
- ‘Royal Red’ has long reddish-purple flowers and is extremely attractive to butterflies.
- ‘White Profusion’ is the most common white flowered cultivar and is very hardy.
Compact Cultivars (less than 6 feet tall):
- ‘Ellen’s Blue’ is a dwarf form (4 feet) with blue-violet flowers.
- ‘Nanho Blue’ has mauve to indigo blue flowers.
- ‘Summer Beauty’ has deep, rose-pink flowers on a compact plant (to 4 feet) with silvery foliage.
- ‘White Ball’ is considered the most dwarf butterfly bush, maxing-out at about 3 feet tall. White flowers cover plant all summer.
Buddleja fallowiana: This is one of the best butterfly bushes for foliage interest. The leaves are 2 to 4 inches long and heavily felted, giving a decidedly silver-gray overall appearance. Plants can reach 10 to 15 feet tall, but can easily be maintained lower. Flower heads are white to lavender and 6 to 8 inches long. ‘Alba’, the most commonly seen cultivar, is more compact than the species, with white flowers.
Sageleaf Butterfly Bush (Buddleja salviifolia): This species is grown primarily for its foliage. It has highly textured leaves that are coppery-green. Flowers are a pale lavender and not especially showy. It is a large shrub (15 to 20 feet tall) from South Africa. It flowers on the previous year’s wood and should be pruned after flowering. It is very hardy and may remain evergreen in Zones 7-9.
Alternate-leaf Butterfly Bush (Buddleja alternifolia): This species is a deciduous shrub with alternate leaves unlike other Buddlejas. It is a very hardy, rapid growing, tall plant (13 to 15 feet) with a weeping habit. This butterfly bush produces purple flowers early in the season on the previous year’s wood and should be pruned after flowering.
Lindley’s Butterfly Bush (Buddleja Lindleyana): This butterfly bush has small dark green leaves and lavender-purple flowers. It is a smaller shrub (4-5 feet) with gracefully arching branches and fragrant panicles. This species will spread by suckers to colonize large areas.