Mustard (scientific name: Brassica juncea) is an annual or biennial herb of the genus Brassica. It is a famous specialty vegetable in China. The main lateral roots of mustard are distributed in the soil layer of about 30 cm, and the stems are shortened stems. The leaves are attached to shortened stems, with elliptical, ovoid, obovate, and lanceolate shapes. The leaf color is green, dark green, light green, yellow-green, purple or purple-red. The leaf surface is smooth or shrunken. The edge of the leaf is serrated or wavy, and the whole edge may have lobes of different depths and sizes. The corolla is cruciform, yellow, with four strong stamens, cross-pollinating, but selfing can also bear fruit. The seeds are round or oval, reddish brown or red in color. China has extremely rich varieties and varieties of mustard for seed, leaf, stem, bud and root.