Erysimum is a Brassica which puts it in the same family as broccoli, mustard and cabbage. The flowers are very similar but Erysimum bicolor is a perennial. Erysimum bicolor or linefolium is a low-growing evergreen plant when raised in USDA zones 7 to 9. The bicolor version of the plant is better known as wallflower.
Wallflowers are common garden perennials that bloom early in spring and last until summer-like temperatures occur. Erysimum prefer temperate climates with mild winters. The plant becomes woody as it ages and is a low-growing, spreading shrub. The leaves are slim and striped with white, providing a contrast for the bicolored flowers. The flowers have four petals and come in shades of white and pinkish-purple. Flowers bloom consistently and attract butterflies.
Wallflowers grow best in well-drained soils. The Erysimum originated in Europe and Western Asia but some forms are found natively in North America. The plant grows well in full or partial shade. Dappled shade accentuates the variegated foliage with its play of light. Wallflower is drought tolerant and can grow in rockeries, sandy soils or gravel beds.
Erysimum is drought tolerant after establishment but you will get better appearance and flower production with supplemental irrigation. Wallflower does well in soils that are not acidic. It grows quickly, forming a mat of vegetation that can act as a ground cover. Deadhead regularly to encourage more blooms. Cut the spent flower stems back to the crown of the plant. Cut back the woodiest stems in early spring to promote new growth.
The variegated Erysimum bicolor tends to bloom out early with its rampant flower production. To reinvigorate the plant you may cut it all the way back, but a better method is division. Divide the wallflower every three to four years or as flower production is reduced. Dig it up in early spring and cut the root ball into two or three sections. Each section may be planted as a separate plant. Eventually the Erysimum will die out as it is considered a short-lived perennial.