The house across the street from mine – an ordinary two-storey Victorian terrace owned by an absent landlord – has a buddleia growing from a crack in its parapet. It’s a curiously ambiguous sight. Buddleias, with their energetic cones of purple flowers, are attractive plants, and butterflies love them. Their ability to grow in the most exposed, unpromising locations is inspiring. Thanks to their preference for broken, rocky ground, with no need of human intervention, buddleias are the flowers of ruin – highly visible evidence of neglect, of a problem left unaddressed. Their casual abundance seems almost insolent. They are something that has arrived early from the post-apocalypse. 

Plants can seem like enemies to buildings when they’re slowly pushing cracks wider, trapping moisture against walls or burrowing their roots into foundations and buried pipes. They are swept aside to make way for bricks, stone and concrete; they may get their revenge, but only after the maintaining humans have moved on. However, as Paul Dobraszczyk explains in Botanical Architecture, plants and buildings are almost inseparable – and may, in the future, become almost indistinguishable. 

Botanical decoration is ubiquitous throughout human cultures, from the carved acanthus leaves of classical stonework to the vegetal ironwork of the Art Nouveau. The builders of the tomb of Ti in Saqqarah in ancient Egypt were decorating columns with representations of water lilies about seventeen centuries before the foundation of