Wild mustard (Brassica kaber) is a winter and sometimes a summer annual. At least two distinctly different forms exist: one with prickly hairy stems, one with smooth stems. Otherwise all other characteristics are similar. Wild mustard is distributed widely throughout the United States and is a common weed of nursery, horticultural, and agronomic crops, in particular are small grains and fall-seeded forage crops. It can also frequently be found in fields, pastures, waste areas, and disturbed sites.
Reproduction of wild mustard is by seed. Seeds germinate in late summer, early fall, or spring. Seeds persist in soil for many years and germinate at a depth of 2 cm in soil. Each plant can produce approximately 1200 seeds. Mature plants possess erect flowering stems that branch toward the top with stiff hairs on the lower portions. Flowers, made up of four yellow petals, are produced from May to August at the ends of the branches in dense clusters that elongate with seed maturation.
Wild mustard can be mistaken for wild radish. However, wild radish differs in that it has stiffer hairs on the leaves than wild mustard. In addition, the leaves of wild radish have more and deeper lobes. The root of the wild radish has a distinctive hot radish flavor when chewed. Wild radish is commonly found mainly on the coastal plains of the Northeast; wild mustard is found primarily on upland soils.
Other species of mustard that you may come across include: birdsrape mustard (Brassica rapa), black mustard (Brassica nigra), Indian mustard (Brassica juncea), and white mustard (Brassica hirta).
For information on how to control wild mustard, you can visit Michigan State University’s Weed Science website.
Resource: Uva, Richard H., Joseph C. Neal, and Joseph M. DiTomaso. Weeds of the Northeast. Ithaca: Comstock Pub. Associates, 1997. Print.