Western Wallflower

Family: 
Brassicaceae (mustards)
Description: 

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.

Size: 
Height: 12 to 40 inches.
Habitat and conservation: 
Found on limestone bluffs, glades, rocky, open hillsides, sometimes road cuts, usually in full sun. This is a biennial or winter annual and cannot be relied on to appear each year. It often disappears after a year of a fine display.
Distribution in Missouri: 
Scattered in a broad band through the central portion of the state, uncommon farther south, mostly associated with major river drainages. Cultivated statewide.
Human connections: 
This showy species is cultivated as a garden ornamental, where it does well in full sun and tolerates dry conditions. If you grow it, you must let it reseed or it may not come back the next year. Some European erysimums can grow in loose mortar in walls, hence the name "wallflower."
Ecosystem connections: 
Several insects, including caterpillars of butterflies and moths, eat the leaves, and deer and other mammals browse the foliage. It is likely that a variety of insects visit the flowers.