Mustard is a plant in the Brassicaceae or Cruciferae family, which includes the cruciferous vegetables like broccoli, Brussels sprouts, cabbage, and cauliflower. The family is sometimes referred to as the mustard family, and the plants in it are often rich in vitamin C, as well as recommended for their cancer-preventive properties.
In general, mustard is used to add a piquant, spicy flavor to foods. It does this in a wide variety of ways, in part because the plant has a large number of different forms. There are two basic varieties of the whole seed: white or yellow and brown or Asian. The yellow seed is the larger and less strong of the two, and it is used to make prepared yellow mustard that is often called “American-style.” Brown seeds are used for pickling and in curry, as well as in prepared condiments characteristically used in Europe and China. There is also black seed, but it is not as commonly used.
The seeds can be ground to create a powder that can be combined with vinegar or wine and other seasonings to make prepared mustard, or pressed to create mustard oil, a very hot oil used in stir-fries. This oil is, in fact, a by-product of commercial condiment production in some places.
Mustard greens come from a completely different part of the plant and are used in salads or cooked as a vegetable. They may be boiled, braised, or steamed, and are often combined in dishes with other greens from the same family, such as collards.
This plant also serves medicinal purposes, having been recommended through history for a wide variety of symptoms. The powdered seeds can be made into a plaster that is used as a counterirritant, creating inflammation in one place with the aim of relieving it in another.