Wallflowers Cheiranthus cheiri (or, to give them their more recent name Erysimum cheiri) have been known as naturalised plants in the wild at least since 1548, but were cultivated long before that and probably originated as a hybrid of uncertain parentage of other members of the cabbage family in the eastern Mediterranean. Whatever their origin, they are a feature of old walls over much of Britain and seem to thrive particularly well on crumbling ancient monuments.
The examples above were photographed on the walls of the lovely Jervaulx Abbey in Wensleydale, Yorkshire, which is noted for its diverse wall flora. Garden wallflowers tend to be grown as biennials but 'wild' plants are perennial and often develop a substantial woody stem. They have a remarkable ability to thrive in dry conditions and are at their best when growing on a sun-warmed wall.
The fragrant flowers appear in various shades, from red through to yellow with every hue in between and this example, on the walls of Bamburgh Castle in Northumberland, is a particularly attractive shade of orange.
Most cultivated wallflowers are spring flowering and attract early bumbleebees in search of pollen and nectar but the plants that are naturalised on walls often seem to have a longer flowering period.