ERYSIMUM

(Brassicaceae/Cruciferae). Wallflower. Genus now including Cheiranthus of about 80 species of mainly evergreen perennials, often woody based found on calcareous soil from Europe to N. Africa, W. and C. Asia and N. America. They are cultivated for their often yellow flowers with 4 petals arranged in a cross, borne in dense, corymb-like racemes. Lance shaped, toothed, softly hairy leaves. Ideal for rock garden or wall, front of a sunny border or raised bed. Prefer neutral to alkaline soil. Trim lightly after flowering.