A biennial or perennial that starts flowering on stems 12 inches tall, growing to 40 inches while blooming. Stems single or branched. Flowers are fragrant, ½ across, deep orange or bright yellow, with 4 petals. Blooms April-July. Leaves alternate, stalkless, linear to lance-shaped, slightly toothed.
Similar species: This is the showiest of the 4 Erysimum species in Missouri; the rest are introduced. Bushy wallflower (E. repandum) has much smaller petals; it is a common perennial that often carpets roadsides with yellow March-June. Smallflower wallflower (E. inconspicuum) is aptly named and uncommon. Wormseed wallflower (E. cheiranthoides) also has small flowers and is uncommon.