Red Valerian (Centranthus ruber ssp. ruber) about to bloom from within the sunken foundation well of a former food processing complex in the Ballarat area. Valerian is a garden ornamental of Mediterranean origin that has been sold in Melbourne from at least as early as 1855 (J. and J. Rule strike again), although it only began to be recorded as a naturalised weed in Victoria from the 1980s. The plant colonises both coastal and inland sites, typically in sandy and often quite constrained (eg. rocky) settings.
In this regard, the species is not out of place in the location pictured, where alkaline geology (a former goldfield!), highly constrained concrete and masonry context, and what we can assume is sandy substrate fill / windblown deposits combine to effectively simulate the environmental conditions in which this environmental weed thrives in Australia. This pattern is also consistent with its weedy habit in its home range; its tendency to establish on old stone walls, roadside verges and cutting is apparently well-appreciated in Southern Europe, and in England where it has also naturalised. Although the photographed colony is in Ballarat, the plant has been recorded at various sites within the Melbourne metropolitan, and I fully expect some Valerian to make a return appearance on the channel in future.