Western wallflower is the showiest of Missouri’s wallflowers. It grows up to 3 feet tall on limestone bluffs, glades, and sometimes road cuts, mostly in our central counties. The bright yellow to deep orange, fragrant flowers make it desirable garden subject.
Western wallflower is a biennial or perennial mustard that starts flowering on stems 12 inches tall, growing to 40 inches while blooming. The stems are single or branched.
The flowers are fragrant, ½ inch across, bright yellow to deep orange, with 4 petals. The flowers are in a dense, rounded cluster.
Blooms April–July.
The leaves are alternate, stalkless, linear to lance-shaped, and slightly toothed.
The fruits are long, narrow pods (siliques) to 3½ inches long, erect or ascending; they mature, first, at the bottoms of the flower clusters, while new flower buds continue to open at the top of the cluster.
Similar species: Several mustard species have clusters of yellow flowers. Among its closest relatives, this is the showiest of the four wallflower (Erysimum) species in Missouri; the remaining three are introduced:
- Bushy wallflower, treacle mustard, or spreading wallflower (Erysimum repandum), has much smaller, light yellow to yellow petals; it is a common weedy perennial that often carpets roadsides with yellow March–June.
- Smallflower wallflower (Erysimum inconspicuum) is aptly named for its small, light yellow to yellow flowers and is uncommon.
- Wormseed wallflower, or wormseed mustard (Erysimum cheiranthoides), also has small, light yellow to yellow flowers and is uncommon.
Height: 12 to 40 inches.
Scattered in a broad band through the central portion of the state, uncommon farther south, mostly associated with major river drainages. Cultivated statewide.
Habitat and Conservation
Occurs 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 the year after a fine display.
Status
Native Missouri wildflower.
Human Connections
This showy species is cultivated as a garden ornamental, where it does well in full sun and tolerates dry conditions. It can be naturalized in wildflower gardens and also does well in rock gardens. If you grow it, you must let it reseed, or it may not come back the next year.
Botanists suspect that some of this flower's occurrences along roadsides may be escapes from cultivation.
Some European erysimums can grow in loose mortar in walls, hence the name "wallflower."
Ecosystem Connections
Several insects, including several types of beetles and the caterpillars of butterflies and moths, eat the leaves.
Deer and other some other mammals browse the foliage, especially early in the season, but as the plants mature, their bitter chemicals probably prevent them from eating it in large quantities.
A variety of bees, flies, butterflies, beetles, and other insects visit the flowers.
