In Season: Mustard greens are at their peak from January through April. Many supermarkets carry them year-round.What to Look For: Look for leaves with a rich green color. Avoid any mustard greens that are wilted or yellowish. The smaller the leaves, the more tender they will be.How to Store: Wrap unwashed mustard greens tightly and store in the refrigerator's crisper drawer for up to one week. Mustard greens tend to hold sand and dirt, so wash thoroughly before cooking.
Mustard greens have a sharp, radishy bite that's delicious in a bean soup, but, if you like, you can substitute kale or collards. Smaller white beans such as cannellini can be used in place of giant white beans.
Baby spinach and red mustard leaves are more tender and spicy than the familiar varieties of those greens. You can use other spicy baby lettuces, such as chard and tatsoi, or look for packaged blends (sometimes called spring or Asian mix) in many supermarkets.