A native of Eruasia, this annual weed is also known as treacle mustard and bushy wallflower. It is wide spread through out most of the US where it grows on disturbed sites such as along roadsides and railroad tracks, and in fields and vacant lots. Spreading wallflower thrives in fertile, moist soil and full sun but tolerates less.
Stout stems grow from two feet tall from thick taproots. They may be branched or unbranched, are angular and bear hairs. The basal leaves are linear, have toothed, wavy margins and from a rosette about six inches across. The leaves on the stems are similar but smaller, less toothed and wavy. Flowering begins in mid- spring and lasts one to two months. The small flowers are borne in terminal racemes and are ¼ “ across. They are yellow, have four petals, and give way to long slender dry fruits two to four inches in length. Plants reproduce only by seed.
Young seedlings are easily hand pulled or hoed while mature plants are more difficult to pull because of the taproot. Control is best achieved by removing flowers before they set seed since the plant has no other method of reproduction . In extreme cases a herbicide can be used.