wallflower, Mediterranean perennial (Cheiranthus cheiri) of the family Cruciferae (mustard family), particularly popular in Europe, where it flourishes on old walls. An old-fashioned garden flower, it is similar in appearance to the related stock and is also sometimes called gillyflower. The early spring blossoms are often much doubled; yellow, red, and brown are the prevailing colors. Related species are also called wallflower, e.g., the orange-flowered Siberian, or western, wallflower (Erysimum asperum), which occurs both wild and in cultivation in North America. Wallflowers are classified in the division Magnoliophyta, class Magnoliopsida, order Capparales, family Cruciferae.