Typical areas Buddleia invades are quarries, urban wastelands, railways, gravel workings, and building sites. In the UK it has spread by wind borne seeds, following the low pressure drag created by trains, throughout the rail network past and present.
Here the loose surfaces of stone and soil embankments form a happy substitute for native slopes and screes, and the thickets formed can encroach on safety zones and hamper access for maintenance etc.
Much damage is also caused to built structures in the railway environment, where any minute crack or softening of mortar, which can admit a seed, is as suitable for germination and growth as any fissure in a rock face. Deeply penetrating and thickening roots and woody stems soon force masonry apart to costly effect.
As with Japanese Knotweed and Himalayan Balsam, the denudation of the under storey of native plants renders banks susceptible to erosion in times of flood.