Brassica nigra or Black Mustard is cultivated for its seeds which are used as a spice. It is an annual weedy plant.

The small hard seeds vary in color from dark brown to black. They have almost no aroma. The seeds are usually thrown into hot oil. When they pop, they release a characteristic nutty flavor. The seeds have a significant amount of fatty oil.

Ground seeds of the plant mixed with honey are widely used in eastern Europe as cough suppressant. In Eastern Canada, respiratory infections were treated ground mustard seeds mixed with flour and water.

The plant itself can grow from two to eight feet tall and have small yellow flowers, with four petals each. The leaves are covered in small hairs; they can wilt on hot days, but recover at night.

Since the 1950s, India mustard has become more popular than black mustard since some cultivars of India mustard can be mechanically harvested efficiently.