When the sun shines these lush and fragrant panicles (each florescence consisting of many hundreds of tiny flowers) attract the attentions of a wide variety of insects, but especially nymphalid butterflies, such as peacock, red admiral, small tortoiseshell and painted lady, large & small white butterflies, as well as many moths, bees and hoverflies.   It is not without reason that it is also known – and sold in the garden trade – as butterfly-bush.  And in the right circumstances one bush can attract hundreds of butterflies over a day.

Buddleia flourished in the bomb sites of London during the 1940s and ‘50s, and is now widespread and common across the capital, found in gardens and parks, but more typically the scruffier parts of town – wastelands, railway linesides, scrapyards and other unkempt curtilages of business parks, transport corridors and derelict land, where it is almost ubiquitous.  A woody shrub, buddleia is often found as individuals, but when space and conditions permit, it can and will quickly proliferate forming dense scrappy clusters and in some conditions extensive stands, almost impenetrable forests reaching five metres high, often in association with silver birch, goat willow, and bramble. It has made its home here and other conurbations around the country.

A garden escapee

But why?  The buddleia most commonly encountered is a native of western China, and first arrived in Britain in the 1890s. It was first ‘discovered’ by a European in the mountains of the Chinese-Tibetan borders in 1869, by Père (Armand) David, a missionary and zoologist, whose name is referenced in buddleia’s scientific name B. davidii. [2] Another French missionary sent specimens back to Europe some 20 years later; these didn’t fare well. But a Parisian nursery firm, Vilmorin, developed a more vigorous variant and launched it as a new plant for gardens in 1893.

However, this species wasn’t the first buddleia to arrive here. Another, now known as B. globosa, had arrived in England in 1774, brought in from Chile by an unknown plant collector [3], prompting one nursery tradesman to call it the ‘Globose Buddlebush’, a yellow-flowered plant with wingless seeds, after Reverend Adam Buddle who, as an amateur botanist, had been posthumously honoured by Carl Linnaeus in his description of the Buddleia genus. But it was the Chinese species that eventually took root.

Buddleia was first sold in Britain from 1896, after stock was acquired by Kew Gardens, and its vigour and attractive flowers made it popular.  It also jumped the fence pretty quickly, helped by its tiny, double-winged seeds, easily carried by wind and the air-currents of rail and road traffic.  It was first recorded growing wild in Britain in Merionith, eastern Wales, in 1922.  Its native habitat is rocky and shingly river valleys (its thickets there once described as a ‘harbourage for tigers’). Closer inspection of what it prefers in London suggests that concrete, mortar in brickwork and rubble, limestone used for paving and kerbs, and general free-draining rubble all provide similar biochemical characteristics to those Chinese river valleys which buddleia thrives on.

A burden on buildings?

Indeed, buddleia’s ability to grow quickly and thrive on mortar means that it can grow on buildings and quickly penetrate cracks in brickwork; if unmanaged it starts to undermine the integrity of buildings, including historic and listed structures.[4] For this reason buddleia is considered invasive and in some places very problematic. Whilst is it listed as an Invasive Non-Native Species (INNS[5]) buddleia is not, somewhat remarkably, listed on Schedule 9 of the Wildlife & Countryside Act 1981 (as amended), which is aimed at restricting the proliferation of damaging species and includes some notorious plants such as Japanese knotweed, giant hogweed, Himalayan balsam, and floating pennywort. Buddleia’s propensity to damage infrastructure rather than crops and the fact it enjoys popularity as an ornamental garden shrub has probably been its saving grace legislatively. Yet it is estimated to cost £1m a year in the damage it can cause to buildings, and is considered a destructive weed by Network Rail. Whilst there are valid reasons to list it on Schedule 9, the costs and means to enforce its control and removal are likely to be highly significant – whose problem would it be?

A nectar power-plant

A member of the figwort family (along with foxgloves, toadflaxes and speedwells), there are 140 species of buddleia worldwide. Three are found naturalised in London; the widespread B. davidii (often sporting a variety of flower colours from white to deep mauve), the ‘original’ B. globosa (‘orange ball-tree’), first recorded wild here in 1964, but not common outside parks and gardens, and B. alternifolia (alternate-leaved butterfly-bush, with long drooping panicles), first recorded wild, in western England, in 1979.

Buddleia provides an important, and obviously seductive, nectar source for adult butterflies, moths and other insects. As many wildflowers have become rarer in the wider countryside, its abundance helps these adult insects in urban areas – almost like a fly-by junk-food station. However, it doesn’t provide any food source for larval insects or other animals (although goats will browse it), and the grey-green leaves cast a dense shade which can crowd out larval food plants especially on some wastelands, rough grasslands and valuable chalky habitats.

The attractive purplish panicles start rusting brown in August as the seeds mature which then start to drop in their tens of thousands to be dispersed by the breeze, and by the autumn buddleia’s stark skeletal fountains of brown stems highlight its deciduous nature. If we want to keep it in check, cutting it before the seeds mature is the ideal time to do so; if not those seeds will soon find ideal nooks and crannies in which to germinate the following spring. Indeed, the seeds can remain viable for three to five years in soil, and any cut stems can sprout again, so recognising the vigour of this amazing shrub is important if we wish to protect some wildlife habitats buddleia can thrive in. And if we wish to support butterflies and moths in our garden or parks, there are more appropriate species to choose from.[6]  

References:

[1] Both spellings are used.

[2] His name was also given to a deer of the locale; Père David’s deer Elaphurus davidianus, of which only about 2,000 survive, mostly outside China (where it has recently been reintroduced after becoming extinct in 1865).

[3] It was first described by Professor John Hope, a Scottish botanist, in 1782.

[4] In this sense it is usually far more damaging than ivy that uses its aerial roots to ‘hang on the surface’ of brickwork in order to obtain water.

[5] See GB Invasive Non-Native Species Secretariat: www.nonnativespecies.org/

[6] www.wildlondon.org.uk/actions/how-attract-butterflies-your-garden