Buddleja davidii

Buddleja davidii

Buddleja davidii is a flowering woody shrub widespread in temperate climates globally. Originally native to the Sichuan and Hubei provinces of central China, the plant was first introduced to Europe in the 1880s as an ornamental garden perennial with vigorously flowering summer blooms known for attracting butterflies and bees. Its small and light seeds can be easily borne by the wind, which has seen the plant spread widely and unpredictably, including taking root in the mortar of neglected or abandoned buildings and waste ground around urban centers. As a result, the plant is often classified as an invasive species, though it continues to be cultivated by gardeners.

Botanical characteristics

The tree-like shrub is semi-deciduous, with leaves shed in the autumn that are immediately replaced with new, smaller leaves that persist until the following spring. It grows quickly, often up to two meters in a year, and has a high degree of plasticity to its form, depending on the terrain where it has taken root.

Its leaves are dark green with a serrated edge and very fine hairs on the underside. The plant's small flowers are generally an intense purple or lilac in the wild, whereas cultivated varieties can be red, white or yellow, with an orange interior. The flowers cluster in thick inflorescences that can extend for up to 30 cm at the end of the plants' branches, forming distinctive cone-shaped panicles. The flowers have a strong peppery, honey-scent and act as magnets for butterflies when they bloom in summer, lending the plant one of its informal names, 'butterfly bush'.

The small seeds of Buddleja davidii are brown, with thread-like 'wings' on either side of a thicker centre. They are usually around 3 x 0.5 mm in size. An individual buddleja plant can produce up to three million seeds in a year, which are highly-dispersible over a large area in a short space of time.

Flourishing on abandoned buildings and wasteland

Taking root in reinforced concrete wall

Buddleja davidii is classified as an invasive species and a threat to native plants in the temperate climates of coastal North America, Europe and New Zealand. The plant's tolerance of a wide range of conditions and ability to quickly produce seeds has seen it spread from cultivated gardens to wild or disturbed lands such as road cuts or new development sites.

The plant first naturalized on a wide scale in Europe in the 1930s and 40s when the destruction of cities during World War II provided suitable habitats in the form of building rubble for dense buddleja thickets to become established. The plant feeds on lime-rich mortar and can use the fissures between bricks to gain hold, able to thrive on minimal nutrients once established. One of its original natural habitats in China was on limestone outcrops. As the plant takes hold, its root systems can weaken masonry and brickwork as they grow, causing potentially costly repair bills or even rendering a property unstable. Buddleja davidii also thrives in quarries, urban waste grounds, abandoned cultivated areas, and along transport corridors, where its seeds can be spread by trains and cars.

The plant's increasing ubiquity across derelict inner-city sites and around the edgelands of industrial infrastructure have seen it embraced by urban geographers.

Lower Garfield Street, Belfast

Belfast-based architect and urban historian Declan Hill has lectured on buddleja and hosted walking tours around abandoned or neglected sites in Belfast city centre, in search of the most luxuriously blooming examples.

Artist Aoife Desmond's Buddleja Forest is a 2012 film work that overlays Super 8 mm photography of buddleja plants and the urban habitats they have colonised with a series of interviews and audio recordings with botanists, an architect and a herbalist.

Eoin O’Mahony and Stephen Rigney, in their online mapping project of brownfield sites in the north inner-city of Dublin, view buddleja as a positive emblem of disorder in the context of planning processes overdetermined by the exchange value of derelict property and sites:

"Buddleia, and the sites on which it grows, echoes Mary Douglas’s two conditions for people and things being out of place: ‘a set of ordered relations and a contravention of that order’." The out-of-placeness of both buddleja and the derelict sites it makes its home has a productive capacity, O’Mahony and Rigney insist, in that it contravenes the assumption of an economic order ceded to formal planning processes centering on permanency. "When we speak about a set of ordered relations for the city, whose order are we talking about?"