Mustard seeds come from a cruciferous plant related to broccoli, cauliflower and cabbage. They can be white, yellow, brown or black. The taste is bitter, spicy and pungent and can be very loud. Usually the darker the seed the more loud and spicy. More than half of the global supply of mustard seeds comes from Canada. They are used frequently all over the world to bring flavor to casseroles, marinades, dressings, sauces, dips, pickles and ferments.