A commonly grown large shrub with an open airy habit. Noted for its vigorous growth and fragrant flowers. Loved by insects and butterflies who seek out its sweet nectar. Buddleias are prolific self seeders, so they can often be found growing wild on wasteland and along hedge rows in the UK.
Botanical Name: Buddleia or Buddleja
Common Names: Butterfly bush, summer lilac
Foliage: Semi-evergreen or deciduous grey/green leaves, usually felted.
Flowers: The common forms have long arching spikes of mauve or purple fragrant flowers (red, pink or white forms are also available). Other species produce round globes of yellow/orange flowers or drooping branches lined with flower clusters.
Flowering Period: Late summer to autumn.
Soil: Moist but well-drained soil (chalk, clay, sand or loam). Any pH.
Conditions: Full sun or partial shade. South, east or west facing aspect, in an exposed or sheltered location.
Type: Shrub or small tree.
Hardiness: Hardy in all of the UK.
Easy to grow and ideal for wildlife gardens as they attract butterflies, especially tortoiseshell and red admiral.
Plant in the autumn or spring. Best positioned in full sun but will tollerate some light shade. Buddleias do well in rich loamy soil but will tolerate poor soils, even chalky soils. Most forms are fully hardy in the UK. However, if affected by frost they can be cut back and regenerated.
An ideal plant for the mixed shrub border or as a foil or background for other flowering plants. It can be grown as a specimen plant on its own or together in a small clump (depending on garden size). The common varieties grow quickly to form large bushes but many drawf cultivars are now available for the smaller garden.
Water thoroughly during dry weather until well established. Mulch with organic matter in spring and apply a general fertilizer designed for shrubs.
Pruning depends on flowering time. Fast growing species that flower on new wood (late flowering) should be cut back hard in the spring, to within a few inches of the previous year's growth. Forms that flower on old wood (early flowering) should be pruned lightly after flowering - by removing some of the older stems, plus any damaged or unwanted growth.
For example: late flowering forms which flower on the current years growth, need to be pruned hard in the spring before the new growth starts. Earlier flowering forms such as B. globosa should be pruned just after flowering. B. alternifolia does not require pruning but it can be tidied-up or confined by removing some of the old wood after flowering.
Note: Buddleia davidii can be highly invasive. It produces an abundance of small seeds that can easily spread across large distances. It will grow virtually anywhere, even in cracks in paving and buildings and can become a blight in the wild. If you have one, or are considering planting one, deadhead regulary and prune it hard back as soon as the flowers have faded, which will help to prevent it self seeding, and dispose of the prunings properly.
Generally disease free. Susceptible to attack by capsid bug.
Take semi-ripe cuttings of cultivars in summer or hardwood cuttings in autumn. Root in a free draining sandy compost, under the protection of a cold frame.
Seed of common varieties can be sown in the open ground in spring.
Buddleia alternifolia is a deciduous form with gently drooping branches, lined with clusters of fragrant flowers. It will eventually grow to form a large shrub that requires plenty of space. Height to 20ft (6m). Available from Thompson & Morgan.
Buddleia davidii is a large fast-growing deciduous shrub, with long arching shoots and lance-shaped grey/green leaves. Height to 10ft (3m). The common form has purple flowers from mid to late summer. B. davidii 'Royal Red' is a rich rose-red form, B. davidii 'Pink Delight' is a pink form, B. davidii 'Black Knight' has dark purple flowers and B davidii 'White Cloud' and 'White Profusion' produce pure white flowers. Available from Thompson & Morgan.
Buddleia 'Flower Power' is new and very attractive colour changing form. The opening buds change from orange to yellow then purple. Height to 5ft (1.5m). Available from You Garden.
Buddleia globosa (Orange Ball Tree Buddleia) is a large, semi-evergreen, early flowering form. It has small orange ball-shaped flowers and attractive dark green foliage. One of the hardiest species in the UK and good for seaside gardens. Available from Gardening Express.
Buddleja Harlequin is a variegated form with green deciduous leaves that have cream coloured margins. Reddish-purple flower spikes. Available from Gardening Express.
Buddleja x weyeriana 'Sungold' is a golden yellow flowered variety. Vigorous growing deciduous shrub. Height to 13ft (4m). Available from Gardening Express.
Buddleja 'Buzz' is a low growing mixed variety, where three coloured varieties are grown together single container, which mix to produce a compact bush that produces fragrant, indigo, ivory and pink flower spikes. Available from Thompson & Morgan.
Buddleia Tricolour is also a mix of three separate plants (white, purple, mauve) in one container to create a mixed bush. Very hardy and easy to grow. Height to 5ft (1.5m). Available from You Garden.
Buddleia Free Petite Tutti Fruitti is a dark pink dwarf form that flowers from early Summer to early Winter. Height to 2ft (65cm). Available from Gardening Direct.
Buddleia Morning Mist (syn. Silver Anniversary) is a low growing silver leaved form topped with scented white flowers. Available from Gardening Direct.
Buddleja 'Blue Chip' a compact hardy, deciduous, shrub that is ideal for patio pots and low hedges. Fragrant blue flowers from June to October. Height and spread: 2ft (60cm). Available from Thompson & Morgan.