Buddleja davidii is native to rocky habitats in China. Introduced to gardens in this country in the nineteenth century it rapidly seeded and spread into suitable environments like the clinker of railway tracks. Seeds are carried far and wide in the wake of trains and the disturbed ground created by 'works on the line' is conducive to the establishment of certain species.

 A good many invasive plants from around the world beautify the railway network with drifts of colour: Ragwort, Red Valerian, Rosebay Willowherb, Michaelmas Daisy, Goldenrod etc. Having said that all this vegetation is not without problems for the running of trains.