This naturalized annual weed was introduced from Europe. Single or multiple stems grow to 2 feet tall, with lance-shaped, stalkless leaves towards the top of the plant (C). The small white flowers have 4 petals, forming a terminal cluster (raceme)(A,C). The distinctive, notched oval seed pods (silicles)(B) develop on stalks below the lengthening flower cluster (A).

This plant is identified by its characteristic oval seed pods (1/3 inch) with deeply notched tips.  A similar mustard, Shepherd’s Purse (Capsella bursa-pastoris), has triangular notched seed pods; another, Peppergrass (Lepidium densiflorum), also has rounded seed pods, but they are much smaller (1/6 inch) and less deeply notched.