Chugging up on the train on the way to Charing Cross I lost count of the Buddleia davidii seedlings clinging tenaciously to the side of the tracks and in cracks in the mortar of old Victorian buildings. They can find a foothold in anything that resembles their native conditions of rocky screes and dry shingle beds. Some may think it a rather plain weed and hoik it at the earliest opportunity but these scruffy individuals are providing a fantastic source of nectar for beneficial insects and our urban butterflies. Buddleia davidii were introduced from China in the nineteenth century, and whilst it is just one of about 100 species of buddleia, it is the most attractive to butterflies, ladybirds, lacewings and all manner of beneficial insects, and as there are so many good cultivars, it seems a good idea to talk about them in particular.
They are the easiest of plants as long as they have sunny conditions and well drained soil and they can withstand pretty dry conditions and are ideal plants to grow in coastal regions.
Buddleia davidii put on a massive growth spurt in the spring and the flowers appear on the end of the stems of this year's growth. As far as pruning is concerned, we used to do it in February but of course the later you leave it, the more likely it is that flowering will coincide with the emergence of butterflies.
Give the plant a serious haircut in late March or early April and take it right down to about two feet from the ground, cutting the stems above a pair of new buds making a slanting cut as you would with a rose. Unpruned buddleia become leggy and full of unproductive woody stems. Pretty hideous actually, and they don't have the longevity of a plant that is regularly tamed in the spring. Give the plant a good mulch after pruning and then perhaps, to encourage flowering, apply a potash-based, slow-release fertiliser. Once the plant is in flower, regular deadheading will encourage new blooms and increase the flowering period certainly producing a second flush and sometimes a third.
But which ones to grow? There are now hundreds of cultivars and a good way to choose one to suit your garden would be to visit one of the National Collections in August to see the different forms, colours and sizes. A lot, of course, depends on the size of your garden and whilst some of them grow to enormous heights like the popular and quite stunning B. davidii 'Black Knight', there is now the new 'Buzz' collection which is great for smaller spaces and pots. Try 'Buzz Lavender' or 'Buzz Ivory'.
Buddleia davidii 'Dartmoor' AGM
I absolutely love this plant. It is somehow softer than the usual cultivars in that, rather than the more common cone shaped panicle at the end of a stem, the inflorescences are broader and less uniform. The flower itself is a soft purple, highly scented, and the shrub is absolutely covered in flowers in late summer. The gardeners at Sissinghurst keep their specimen to a perfect height so that you can see the flowers (and its accompanying butterflies) close up as you pass by on the path towards the Rose Garden.
Buddleia davidii 'Black Knight' AGM
Everything about this plant is dramatic, huge, long trusses of flowers in a wonderful deep violet and scented too. When mature it can put on growth at quite a pace and reach heights of four metres so put it at the back of the border where it will soar above everything else and provide a dramatic 'nectar bar'.
Buddleia davidii 'Lochinch' AGM
The first gardening book I ever read, as did quite a few of my gardeny friends, was Robin Lane Fox's Better Gardening. I still have it and had a look to remind me what his favourite buddleia might be and it was this one. I'm not surprised as this is a very decorative plant as its leaves are silvery and thus it looks good through the winter and then in the summer after, of course, you have given it its haircut and it has come back. It combines silver leaves with the softest violet blue flowers with an orange eye. They're highly scented too. 'Lochinch' works well in a white border or a predominantly blue border combined with companion plantings of blue perennial geraniums, nepetas or lavenders. Gorgeous.
Buddleia davidii 'Pink Delight'. AGM
Another lovely buddleia, widely grown, with a unique and complex family tree which includes 'Lochinch' in it. The buds are a pretty claret colour and they then open up to long clear pink flowers on arching stems. Height wise, this one can get to about five feet and its flowers are complemented by its leaves which emerge in spring as a soft silver and then change to a gentle green as the season progresses.
Buddleia davidii 'Blue Horizon'. AGM
A large buddleia reaching three metres at maturity, but with sapphire blue flowers. Who could resist that? Described as the bluest of the buddleias, I see that the highly knowledgeable and discerning Bob Brown of Cotswold Garden Flowers (whose catalogue is so entertaining to nerdy plantaholics) says that if he grew only one buddleia it would be this one. It is fairly recent to cultivation but has already been awarded an AGM by the Royal Horticultural Society.
Buddleia davidii 'Sugar Plum'
Compact, with very upright panicles of a velvety bright plum combined with dark leaves. This is a recent introduction and was bred by Longstock Park Nurseries which holds one of the National Collections of Buddleia. It's ideal for the border or can be grown happily in a container.
Two of the National Collections of Buddleia are held at:
• Longstock Park Nurseries. 01264 810894 email@example.com
The nursery is also home to a National Collection of Clematis and Penstemon and is owned and run by Waitrose!
• The Lavender Garden Nursery. Ashcroft Nurseries, Kingscote, Tetbury, Gloucester, GL8 8YF. 01453 860356 mailto:firstname.lastname@example.org
Sue Whigham can be contacted on 07810 457948 for gardening advice and the sourcing and supplying of interesting garden plants.