Blue mustard is a winter annual that germinates in the fall and produces a rosette with deeply lobed leaves, similar in appearance to a dandelion.
Blue mustard bears purple or blue flowers at the top of the plant in March through April. Leaves on the flowering stems are coarsely toothed and have wavy margins. The plant may grow from 1 to 1 1/2 feet in height. Two-inch long, bean-like seedpods (siliques) that resemble "beaks" mature in early summer.
Herbicides are most effective if applied before weeds start to bolt in the spring. In the spring, while it is actively growing, this weed can be controlled with an application of 2,4-D.
Photographs: Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010