Erysimum cheiri, also known as English wallflower, is a bushy evergreen biennial. Depending upon their variety, these flowers grow from 8 to 18 inches tall, producing dense clusters of fragrant cross-shaped blossoms in brown, cream, red, white and orange. Wallflowers need protection from winter weather and several diseases, including clubroot. The North Carolina State University Extension explains that clubroot is serious disease; not only does the disease cause plants' roots to deform, it affects the soil in the fields for years.
Select a location for the plants that will protect them from severe winter weather. They can be planted in containers and brought indoors during winter.
Protect the flowers from clubroot disease. Add lime to the soil before planting to reduce the effect of the disease or plant the wallflowers in clean containers with sterile potting soil. Destroy any flowers affected by clubroot.
Watch for bacterial wilt, a fungus that causes the leaves to lose their color, wilt and die. Remove any affected flowers and destroy; do not add to the compost.
Watch for white rust on the wallflowers. This disease forms white, pus-filled spots on the leaves, which may shrivel. The spores can be transported to other gardens. Remove affected flowers and destroy them.