Wormseed mustard is an annual herb that grows to about 1 m in height. It has multi-branched, reddish stems covered with small, sharply toothed leaves. It bears numerous small yellow flowers in clusters along its stems. Following the flowers, it produces thousands of tiny black seeds in small fruit clusters. It is easily spread and re-grown from the numerous seeds it produces which is why some consider it an invasive weed. The whole plant gives off a strong and distinctive odor.