How to grow Buddleja (Butterfly Bush)

Buddleja is an easy to grow, summer flowering deciduous shrub.

Although there are evergreen varieties of Buddleja, the main varieties on sale and growing in the UK are B. globosa, illustrated in the centre image, B.alternifolia, B.davidii and Buddleja x weyeriana far right illustrated 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. 

 Overall, one of the most commonly grown is B.davidii (image above left) which is deciduous, and fast growing. It makes a large shrub, up to 2.5-4m with 5m spread.   

Buddleja are hardy, B. davidii H6  and alternifolia H4 are fully hardy, B. globosa H5 and b.weyeraina H6.

Buddleja has panicles of flowers, often scented or aromatic, and which are attractive to insects and butterflies. Each panicle has hundreds of tiny flowers and the flower panicles are large so that a Buddleja in bloom is a showy sight. Buddleja is a magnet for pollinators and butterflies. Buddleja will attract many butterflies, in the image left a single panicle has 3 butterflies on it.  An excellent combination is to plant with Buddleja is Oregano and Sedum, which will create a butterfly paradise. B.davidii is fully hardy even for cold exposed areas and also suitable for coastal gardens

Growing and planting Buddleja

Buddleja flower best in a sunny spot, which is also where the butterflies like to find them.  Buddleja is easy to grow but a little maintenance in terms of an annual prune will keep Buddleja in check, and flowering well. Buddleja are not fussy as to soil types, growing especially well on chalk and lime soil. Easy to grow even on poor soil. 

There is a significant variety in the size of Buddleja; the popular 'Black Knight' spreads quickly and can reach 3 meters, and there are many species which are more compact, and dwarf and patio varieties have been developed , such as B. 'Nanho Blue'. Check out the overall size of the shrub to make sure there is plenty of room to expand after planting. 

Recently Buddleja has had bad press as being invasive, because it does self seed, and this can be a problem if your garden is near an area of natural beauty or conservation. If this is a concern, dead-head the flowers, which will prevent it from setting seed.

Best Varieties of Buddleja to Grow

This denotes RHS award of garden merit always a good starting point when selecting a shrub or plant.

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.

How to prune Buddleja

Buddleja davidii will flower best if 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. Buddleja davidii should be pruned 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. If it is not pruned, over time it will get very large, and the flowers smaller and fewer.

The other common types of Buddleja, B. alternifolia  and B. globosas are pruned differently because they flower on "old wood" . If they were pruned in early spring, this would result in cutting off the stems carrying the flowers. These types of Buddleja are lightly pruned after flowering mid  summer onwards.  

For pruning purposes, the different types of Buddleja need to be distinguished.  With B.alternifolia  and globosa do not prune hard, just cut back the flowering stems, to keep to shape.

Buddleja davidii after Pruning

neatly pruned Buddleja davidii
neatly pruned Buddleja davidii
Close up of neatly pruned Buddleja davidii
Close up of neatly pruned Buddleja davidii

For pruning purposes, how to tell which Buddleja you have?

The distinct weeping form of Buddleja alternifolia is how to distinguish it from Buddleja davidii

The flowers on buddleias davidii and alternifolia are similar. The difference is that b. alternifolia has alternate leaves. In addition, it has a distinct weeping shape, and its flowers are light mauve, appearing in late spring and early summer. The leaves have a silver tinge and it is less common than B. davidii.

B.davidii flowers later in the year, from July/August onwards, and flowers in many colours which include light mauve, but also many shades of purple, dark purple, red, and white.

It is arching in habit as compared to weeping. If you are not sure which Buddleja you have in your garden, the flowering time is the best indicator.


Buddleja is easy to grow and tagged green wheelbarrow. However, their ease of growth makes up for this because they require little maintenance, particularly in terms of pruning back in late winter.