Onions are vegetables that belong to the lily family of plants. They are grown for their edible bulb, and most often used to flavor a variety of foods.
Onions fall into one of two categories: green or dry. Green onions are small onions that are harvested while the tops are still green and before the bulb has matured. Dry onions are mature onions, harvested when their green tops have dried down and layers of papery thin skin have formed over the firm juicy flesh.
Dry onions come in a wide variety of shapes and sizes, ranging from small, round pearl onions to larger, spherical-shaped Spanish onions. There are two types of dry onions: fresh (spring/summer) onions, which are also referred to as sweet onions, and storage (fall/winter) onions. Sweet onions have higher water content than storage onions and are served either raw or cooked.
Michigan raises primarily yellow and red dry storage (fall/winter) onions. Storage onions have a higher sulfur content and less moisture than sweet onions, meaning they can be kept in storage for longer periods of time. The storage onion is used in cooking, providing a sharper and more flavorful taste than sweet onions.
Yellow onions are an all-purpose, dry variety of onion, readily available year-round. They are globe-shaped and range in size from golf ball- to softball-size, with yellow flesh and golden, papery skin. Approximately 80% to 90% of onion production in the United States is devoted to yellow onions.
These onions are most commonly used in recipes to add flavor. When raw, yellow onions are pungent (more than a white onion), and the high sulfur content may cause tears in one’s eyes when chopping. When cooked, they provide a sweet and rich onion taste, making them a good choice for heated dishes which require a distinct onion flavor. Sautéed yellow onions turn a deep brown color and can be added as a complement to a variety of dishes, such as casseroles, savory pies, quiches, stir-fries, pizzas, and soups. Yellow onions are also good for caramelizing.
Red onions are a variety of onion that have purplish-red skin and white rings of flesh outlined with purplish-red. They are medium to large in size and have a mild, sweet flavor and crisp texture. Red onions are good to eat raw and are used to add color to salads. They can also be grilled or lightly cooked with other foods.