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Guardian | brazen buddleia

July 12, 2012

This feature was originally written for the Guardian

Picture the urban scene.  The chimney with a plume of bush, not smoke.  The stuttering guttering, become plant container.  The rubble filled wasteland temporarily knotted with growth.  The brick rail bridge decked with foliage and flowers.  Let us celebrate buddleia’s brazen ways – the way it rampages through unloved urban areas and clings to the side of buildings.

Of course some people hate it.  They declare it an invasive weed and call for a cull.  In natural areas it can strangle out native species and should be controlled, but in concrete deserts surely we should praise its tenacity and the rich nectars it provides to urban insects.  Tamed in the garden it can be a striking butterfly magnet.

Buddleja’s roots

Professor Peter Houghton has been studying buddleia for 30 years, and has spent many an afternoon on a railway siding digging up its peppery smelling roots.  He once had a freezer full of root samples that, when tested, were revealed to have anti-fungal properties.  This could be a way that buddleia protects itself against attack from creatures in the soil.  It’s a plant he continues to be fascinated by, but no longer has in his garden or his freezer.

The manmade urban landscape often mimics buddleja’s natural one of rocky mountain tops and dry shingle. Peter explains that “it occupies an ecological niche in tolerating the high levels of calcium found in mortar.  Buddleia loves well drained soil and is good at conserving water.  The hairs on the underside of the leaves must play a part here, covering the stomata and cutting down evaporation.”

Self-seeding Buddleja davidii was brought to the UK from China in the 1890s.  It became widespread as a weed in Britain after World War Two, rushing like wild fire through freshly exposed bomb sites and reveling in all that exposed mortar and rubble.  It’s now seen growing with abandon in towns and cities across the UK, and beyond.

Peter’s lifelong investigations include looking into buddleja’s use in traditional medicine.  The leaves have been used as a poultice for wound healing in Eastern Asia, South Africa, South America and Mexico.  An infusion of the flowers of Buddleja officinalis, which blooms in January, is used as an eye-wash and to reduce inflammation in Chinese medicine.  It can be found growing in the Chelsea Physic Garden, which showcases medicinal plants from around the world.

Buddleia tamed

Buddleia is fragrant and floral, and can look great in a garden if it’s kept in check.  There are numerous varieties and cultivars available, not just the infamous and fast spreading purple Buddleja davidii that delights and offends in equal measure.

Peter Moore tends to the national collection of buddleia at Longstock Nursery on the Leckford Estate in Hampshire.  He spends 15 hours a week dead heading the bushes in summer.  Like Professor Houghton, he has also discovered that there’s more to buddleia than its (debatable) good looks. “In Chile they sell Buddleja globosa as a tea – a brew I would not recommend” he says.

What he does recommend is growing the tender Buddleja asiatica in your garden – it has panicles of sweetly scented white flowers.  Other favourites include cultivars of the davidii like ‘sugar plum’ (which has velvet burgundy flowers), ‘summerhouse blue’, ‘white wings’ and ‘white profusion’ (which has tiny fried egg flowers).

Small spaces and year round interest

The national collection boasts 15 compact cultivars of Buddleja davidii that would suit smaller spaces.  Peter suggests ‘Camberwell beauty’ (which has branched flower panicles), ‘glasnevin’ (lilac-blue flowers), ‘pink spread’ (deep pink) and ‘marble white’.  If space is limited to a single patio pot, try the dwarf ‘buzz’ versions created by Thompson and Morgan, which come in four colours, or the ‘bluechip’ from the USA.  Another Longstock favourite is ‘silver anniversary’, which looks good in a container or an herbaceous border.

For year round interest, ‘lochinch’ is covered with lavender flowers well into September and has silver-white foliage throughout winter.  Hardy evergreen Buddleja auriculata makes a good wall shrub.  It has fragrant white flowers in autumn and winter, and provides much needed nectar for early emerging insects.  Buddleia is a good choice for wildlife friendly gardeners because it’s so nectar rich, but the RSPB recommend nature fans plant non-invasive Buddleja globosa (which has orange-yellow flowers) rather than prolific Buddleja davidii.

And what, to conclude, of that particular species bad reputation?  “Buddleja davidii is like the urban fox – it’s nice to have something wild in the city but it can be annoying too.  You have to keep it under control in gardens, but it’s nice to see a wasteland covered in it.  It’s certainly one of the most attractive weeds we’ve got, and one of the only ones that’s a bush” says Peter Houghton.  To anyone still convinced that buddleia is nothing more than an invasive weed, Peter Moore says visit the national collection in July or August – “you’ll be bowled over”.

How to grow

Bushy buddleia likes well-drained soil and thrives best in sunny spots.  The shrub can get large and leggy – hard pruning in late March is essential to keep bushes at a manageable size.  De-heading the flowers (as you would a rose) will result in second and even third flushes of flowers and prevent self-seeding.  

Further reading

Look up the RHS 2008-2010 trial report of Buddleja davidii and its close hybrids.

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