Buddleja Key Facts

Buddleja is an easy-to-grow, fully hardy, summer-flowering, (generally) deciduous shrub. It does well in a sunny spot and is disease free and low-maintenance. 

The most commonly grown is B.davidii image, with large purple flowers,which is deciduous and fast growing. It makes a large shrub, up to 2.5-4m with 5m spread. 

Buddleja has panicles of aromatic flowers attractive to insects and butterflies. Each panicle has hundreds of tiny flowers and the flower panicles are large: a Buddleja in bloom is a showy sight. Buddleja is a magnet for pollinators and butterflies. Buddleja will attract many butterflies. In the image a single panicle has 3 butterflies on it.

Buddleja does get a bad press. It is a non native, and considered invasive. It is not formally listed in the UK as invasive, but the sight of it colonising wastelands and railway tracks shows its staying power.

With certain caveats, such as avoiding the most prolific varieties (such as B.davidii), considering sterile varieties, and dead-heading . Buddleja attracts a wide range of pollinators and butterflies. The Butterfly Conservation Trust has a lot to say in its favour, and it's a favourite of the Mullein moth. I grow a clump of stinging nettles at the base, which are attractive to caterpillars of red admiral, comma, painted ladies and small tortoiseshell.

Buddleja flower best in a sunny spot, which is also where butterflies like to find them.  The only maintenance required for Buddleja is an annual prune to keep Buddleja in check, and flowering well. Suitable for almost anywhere in the garden, Buddleja will grow in all soil types, and does especially well on chalk and lime soil. Easy to grow even on poor soil. 

Buddleja davidii will flower best if it is hard pruned in late winter or early spring,  around late Feb/March time. Prune to around  30-60cm down to woody framework, which also helps to check its overall size. It will look sparse when first pruned, but it is best to be bold and it will spring back into life and shoot up. Prune Buddleja davidii when the worst of the weather is over.  Pruning Buddleja is not essential, the shrub will survive if not pruned, but pruning produces the best flowers and keeps it to size. 

The other common types of Buddleja, B. alternifolia  and B. globosas are pruned differently because they flower on "old wood" . If  pruned in early spring, this would result in cutting off the stems carrying the flowers.  For these types of Buddleja all that is required is a light prune after flowering, mid summer onwards.  

This means for pruning purposes, the different types of Buddleja need to be distinguished.  

Whilst most varieties of Buddleja are deciduous, there are a few which are semi evergreen.

Most are deciduous, although there are three semi-evergreen varieties of Buddleja common in the UK: B. globosa, illustrated with yellow, round flowers; B. alternifolia; and Buddleja x weyeriana, illustrated with variegated flowers, which is 'Moonlight'.

B.weyeraina is a cross between Buddleja davidii Magnifica and Buddleja globosa. I think Moonlight,  illustrated, is the most attractive with mauve flowers turning a delicate shade of peach. There is also " Sungold" a predominantly yellow variety, and "Golden Glow" a mix of the two.

Buddleja has many attractive flowering colours all ranging around mauve, pink, purple and white and well-known varieties are: B 'Black Knight' which is dark purple, 'White profusion,' 'Harlequin' pink which also has variegated leaves, and 'Empire Blue'.  All Buddleja davidii are fragrant. B Buddleja alternifolia, which is also deciduous, and has lovely scented lilac coloured flowers in early summer. 

A good starting point is the RHS garden merit shrubs with the RHS awarded of  garden merit logo.

Buddleia davidii Nanho White 'Monite' scented compact up to 1.5m

Buddleia davidii Nanho Purple 'Monum'  around 2.smaller purple flowers

Buddleia davidii 'Black Knight' scented very dark purple up to 3m.

Buddleia davidii 'White Profusion' large up to 4m and scented

Buddleia davidii 'Royal Red' large up to 4m scented red flowers

Buddleia 'Pink Delight' up to 4 m smaller pink flowers

Buddleja davidii 'Darent Valley'

Crocus has a good selection, including Buddleja x weyeriana ( affiliate link)

For a smaller garden, B. ' Sugar Plum' raised by Peter Moore it is a red variety which is compact, growing to around 1-1.5m (3-5ft). Peter Moore has bred many varieties and Longstock park Nursery near Stockbridge in Hampshire houses the national collection, definitely worth a visit during July and August when it will be full of flower, scent and butterflies. 

Buddleja provides lovely later summer colour and looks well planted with other silver foliage plants such as Nepeta, Artemisia, also with tall grasses such as Stipa. There are some very compact Buddleja suitable for containers and patios such as such as B. Buzz, Blue Heaven, and B. morning mist. More compact varieties are being introduced to the market all the time, and the compact varies grow well as container plants.