Erysimum (wallflower) is a genus of flowering plants in the botanical family Brassicaceae, that includes about 180 species, both popular garden plants and many wild forms. The genus Cheiranthus is sometimes included here in whole or in part. Erysimum has recently been ascribed to a monogeneric cruciferous tribe, Erysimeae. This tribe is characterized by sessile, stellate and/or malpighiaceous trichomes, yellow to orange flowers and multiseeded siliques.
Wallflowers are annuals, herbaceous perennials or sub-shrubs. The perennial species are short-lived and in cultivation treated as biennials. Most species have stems erect, somewhat winged, canescent with an indumentum of 2-fid hairs, usually 25 ± 53 cm x 2–3 mm in size, and t-shaped trichomes. The leaves are narrow and sessile. The lower leaves are linear to oblanceolate pinnatifid with backwardly directed lobes, acute, 50–80 mm x 0.5–3 mm. Flowering occurs during spring and summer.