Erysimum Embers — Print

Wallflower — A vibrant factory of chemicals

This common garden plant is an unusual member of the mustard family, Brassicaceae, deriving its name from its ability to grow in loose mortar. This plant was endemic to Mediterranean regions, but escaped and established as a garden plant in Central Europe in ancient times. What makes them so colourful?

Wallflowers grow as an inflorescence (cluster of flowers on stem) with vibrant yellow to red colours, and scents. Colour variations arise from proportions of different pigments, anthocyanidins (orange-red) and carotenoids (yellow), that yield these hues. The floral colours, along with their scent, attract a variety of pollinators—bees, butterflies, beetles, and ants. Recent research has unveiled the genetics behind these colours, revealing how these pigments are produced and shift from yellow to orange-red.

Wallflowers also produce a compendium of chemicals in their flowers, seeds and leaves that served medicinal purposes in ancient times. Not only do they produce glucosinolates (the sulphur compound producing characteristic smells in Brassicas), but they also synthesise cardenolides, both of which allow escape from herbivory. White cabbage butterflies, which can attack other Brassicas, are repelled by the cardenolides in wallflowers. Same family, yet very different.