Alternate-leaved butterfly-bush is a flowering plant endemic to China. It is a sought-after garden plant, particularly in the United Kingdom, due to its mildly fragrant cascade of lilac flowers that attract butterflies in particular. This is where the shrub gets its common name.
I. Appearance and Characteristics
Buddleja alternifolia, known as alternate-leaved butterfly-bush, is a species of flowering plant in the figwort family, which is endemic to Gansu, China.
B. alternifolia is a vigorous deciduous shrub reaching 5 m (16 ft) tall with long, slender, pendulous stems. The leaves are alternate, entire, and lanceolate, 4–10 cm long by 0.6–1 cm wide, glabrous and dark green above. The inflorescences of the plants in cultivation are bright lilac-purple, and comprise flowers so densely crowded in clusters along the branch as to often obscure it. However, specimens from the Tsangpo valley in Tibet originally named B. tsetangensis by Marquand have creamy flowers. Flowering occurs in early summer; the flowers are fragrant, but less so than other buddlejas. 2n = 38.
In its native territory it grows along river banks in thickets at elevations of 1,500–4,000 m (4,900–13,100 ft).
In the West this plant was first described and named by the Russian botanist Carl Maximowicz in 1880. It was not introduced to cultivation in the West until 1915, by Purdom and Farrer.
The species has become very common in cultivation, a popular shrub for the larger garden, and is readily available from most garden centres in the UK. Fully hardy, it prefers a sunny position and loamy soil; pruning should immediately follow flowering. Like most buddlejas, the species is easily propagated from cuttings. Hardiness: RHS H5, USDA zones 7 – 9.
- alternifolia was accorded the Royal Horticultural Society’s Award of Garden Merit (record 674) in 1993.
II. How to Grow and Care
Sunlight
Alternate-leaved butterfly-bush prefers full sun. A minimum of 8 hours of bright sunlight is required if many blooms are desired. Do not plant under trees since too much shade will affect its growth.
Watering
Thriving in its native habitat of rocky riverbanks, alternate-leaved butterfly-bush has adapted to periodic water availability, indicating a preference for well-drained conditions and moderate moisture. Its watering needs are met once every week, ensuring a balance that mimics its natural environment. Typically grown outdoors due to its size and growth habit, alternate-leaved butterfly-bush is deciduous, shedding leaves annually which influences its water uptake during different seasons.
Temperature
Some hybrids of genus Buddleja are less tolerant of cold temperatures. Towards the fringes of their range of hardiness, they may act more like a herbaceous perennial and die back to ground level during the winter. Their rapid growth means this should not pose a problem to blooming. Alternate-leaved butterfly bush (B. alternifolia) is a good choice for cold areas, as it has more hardy roots than most others.
Soil
Alternate-leaved butterfly-bush prefers neutral to alkaline soils that are rich in nutrient. It will tolerate alkaline soils of up to 8.5, ideally within the range of 5.5-7.0. It can cope with most types of soil, even chalk, and is able to grow in coastal areas, as it is tolerant of salt. It doesn’t like heavy clay.
Fertilizing
For optimal health, alternate-leaved butterfly-bush requires balanced, slow-release fertilizers, applied once in early spring and again in mid-summer. Fertilization promotes vigorous growth and abundant blooms. Use sparingly to prevent nutrient runoff and root burn—roughly one tablespoon per square foot around the drip line. Adjust application based on growth; less if alternate-leaved butterfly-bush is thriving, more if it’s lackluster. Always water alternate-leaved butterfly-bush thoroughly post-fertilization to aid in nutrient uptake and minimize root stress.
Planting Instructions
Alternate-leaved butterfly-bush should be planted once the soil has warmed and the last frost has passed. Late spring or early summer would be a good time of year to plant. Dig a hole two to three times wider than the plant’s root ball (a little deeper, if additions are being used). Additions include compost, fertilizer, and limestone chippings.
Limestone chippings are not essential, but can help to keep the plant from suffering due to low pH if the surrounding soil is acidic. It can also improve drainage. Compost can be used to improve the structure of the soil and improve drainage in heavy clay soils.
The use of fertilizer when planting means that the plant should not require more fertilizer for a year or two. Applying it around the roots makes it very accessible to the plant. If the plant must be moved, the best time is late autumn or early winter. At this time, they are not in a period of rapid growth, so are more able to deal with the changes.
Pruning
Pruning should be carried out in early to mid-spring. Earlier in the spring will allow more time for alternate-leaved butterfly-bush to recover, which should result in more blooms. Cut back flowering stems from the previous year to within 1-2 buds of the older, woodier framework of the plant. Remove any thin, dead, or weak growth. Cutting the plant annually back to around 61 cm in height will keep the plant from getting too large.
If the plant is in an exposed and windy site, reduce its height by about half in the autumn to avoid wind damage. Alternate-leaved butterfly bush and orange ball tree both flower on the previous year’s growth, so spring pruning would likely reduce the number of flowers that year. These types benefit from pruning after flowering. Deadheading regularly will encourage flowering.
Propagation
Alternate-leaved butterfly-bush is primarily propagated through cuttings, a method that suits its growth characteristics. To ensure successful rooting, take semi-hardwood stem cuttings at an optimal length, typically between 4-6 inches. Make a clean cut just below a leaf node and remove the lower leaves to expose the stem. Employ a rooting hormone if available to encourage quicker root development.
Plant the cuttings in well-draining soil and maintain consistent moisture without overwatering to foster a hospitable environment for root establishment. With proper care, cuttings take root effectively, enabling the grower to expand their collection of this elegant, butterfly-attracting shrub.
Transplanting
For alternate-leaved butterfly-bush, the cusp of spring is the prime transplanting season, offering a gentle climate foundation for root establishment. Select a sun-kissed spot with well-drained soil to foster growth. Gentle handling is key during the transition.
Repotting
Repot alternate-leaved butterfly-bush every 2-3 years in early spring to support its growth pattern as a graceful, cascading bush. Choose a larger container each time to accommodate its size. Post-repotting, place alternate-leaved butterfly-bush in a well-lit area and water moderately to encourage recovery. Its robust nature simplifies ongoing care, making alternate-leaved butterfly-bush a delightful addition that continuously attracts butterflies.
III. Uses and Benefits
Alternate-leaved butterfly-bush is perfect for shrub borders, foundation plantings, butterfly gardens, or cottage gardens.
IV. Harvesting and Storage
Alternate-leaved butterfly-bush can be used as cut flowers. It has a honey-like fragrance. Cutting the flowers also encourages the plant to produce more blossoms.
