When it comes to growing buddleias (or buddlejas) there’s a wide range on offer and they vary in habit and quality. It’s better to opt for compact varieties rather than the tall rangy ones. These sit better in the garden visually and they don’t lose whole branches in strong summer gales. However, larger varieties of buddleias can be kept compact with hard pruning in March.
When to plant
Plant buddleia in late spring, once the soil has had a chance to warm up – invest in a soil thermometer!
If grown in a container and fairly robust then you can leave planting to as late as August.
Where to plant
In the wild, buddleias tend to grow in rocky ravines so plant them in a sunny position on well-drained soil. They will not perform in soil that retains water in winter.
Buddleias also have a preference for alkaline soil so you may have to add lime to acid soil to alter the pH. Otherwise they will survive in most conditions.
They also make good specimens standing on their own in grass, or against a sunny wall.
Buddleias can also be grown in coastal conditions. Read more about coastal garden plants.
How to plant
Top dress with manure in autumn or sprinkle on an organic feed in late spring to improve the number of flowers.
When it blooms
Buddleia blooms in August (usually a lackluster month for flowering gardens) and Buddleia davidii (or buddleja davidii) produces a mass of tapering flowers on an arching bush of silvery foliage.
Read our guide to August-peaking plants.
Buddleias are a magnet butterflies and moths. The orange-eyed flowers are honey-scented and full of nectar. And although this plant is a Chinese introduction, it is the best plant for attracting and sustaining British butterflies. It can attract 22 native species and every garden should aspire to plant at least one in a warm, sunny position where the nectar can flow.
Find out more about British butterflies.
When to deadhead
Deadhead budleia as the flowers fade to encourage a continuous supply of flower and take off every spent flower at the end of the year to prevent unwanted seedlings.
Buddleias need savage pruning, especially the taller varieties. But care must be taken to do this in late-spring when the hardest weather is over. Prune them in autumn and they can die.
If you’re dealing with an overgrown buddleia, take one half down in one year (in March) and the second half in the following year (again in March).
Read our guide to pruning shrubs.
When to take cuttings
Take softwood cutting in late spring just as the stems begin to harden up a little. Look for new shoots about six inches in length (15 cm) and trim them below the leaf node and nip out the top.
Remove any overlarge leaves and insert your cuttings into a 50% horticultural sand and 50 % compost mixture. You can use hormone rooting powder if you wish.
Water the cuttings with mains water that has been standing (this eliminates chlorine) and cover the cuttings with polythene or glass. They will root quickly and can then be potted up.
Read our guide to taking softwood cuttings.
Pests and problems
Buddleia may be attacked by capsid bug, caterpillars and glasshouse red spider mite.
The silvery foliage of buddleia mingles well with other sun-loving silver plants and these could include the pale-lemon anthemis ‘Susanna Mitchell’, the dark-purple lavender ‘Imperial Gem’ and nepeta ‘Six Hills Giant’.
The dark-flowered forms need a paler companion and the lemon-yellow daisies of Helianthus ‘Lemon Queen’, or the tall delicate daisy, Bidens aurea ‘Hannay’s Lemon Drop’ are tall enough to nudge up underneath and create that contrast.
The pink forms are excellent with darker flowers including the red scabious, Knautia macedonica, and dark scabious, like Scabiosa atropurpurea ‘Ace of Spades’.
But all have an orange eye which can be picked out by planting August-flowering orange crocosmias ('Firebird', 'Star of the East' and 'Severn Sunrise') or the soft-orange dahlia 'David Howard'.
Growing buddleia types
The hybrid ‘Lochinch’ ( Buddleia davidii x Buddleia fallowiana) is one of the best. The small flower spikes are lavender-blue with an orange eye and the small silvery grey-green leaves persist through winter in milder areas, or in sheltered positions. In colder places it loses its leaves - but always returns the following year.
If you require a dainty performer then ‘Nanho Blue’ and ‘Nanho Purple’ are both excellent buddleia hybrids. They reach 1.5 m (4 ft) in height and have long, slender flower spikes the former in indigo blue and the latter in purple. The flower spikes bend very gracefully.
For a ‘heavy-handed’ buddleia choose ‘Dartmouth’ for this magenta-purple flowering form has hand-shaped blooms with several spikes appearing from one ‘palm’. Collected on Dartmoor in 1971 (by a retired American gardener who was holidaying in Devon) cuttings had to be rescued from a rocky ravine. It’s hardy and tall, reaching 16ft (5m) and it can make a real impact on the eye.
If you prefer a traditional buddleia there’s the dark, grape-purple ‘Black Knight’ and this can shine against silver foliage. ‘Royal Red’ is a rich-magenta. But it must be cut back in late-spring every year to keep its shape. ‘Empire Blue’ is also excellent, bearing small flower spikes in true-blue. All three are older, taller varieties.
Best compact buddleias to grow in small gardens
There are some compact varieties of buddleia especially suitable for growing in smaller gardens. They include the pink ‘Peacock’ and ‘Pink Delight’. Both are flower-packed and Notcutts sell ‘Peacock’ plus several more named after British butterflies. They include ‘Purple Emperor’, ‘Adonis Blue’, ‘Marbled White’ and ‘Camberwell Beauty’.
‘Pink Delight’, bred in 1990 in Holland, is the prettiest pink and this compact, fragrant buddleia has long flower spikes and silvery foliage. The one colour I shun is white, simply because the flowers brown as they fade.