ONION  

The onion, Allium cepa, of the family Amaryllidaceae, is by far the most important bulb vegetable. It is used both in its green stage as a scallion, or green onion, and in its mature stage as a bulb--the tightly packed globe of food-storage leaves containing the volatile oil that is the source of the onion's pungent flavor. Thought to have originated in Asia, the onion has been cultivated since ancient times. Present-day cultivars include the Sweet Spanish, Bermuda, and globe onions. Onions vary in color, with white, yellow, and red predominating. Cultivars range from mild and to pungent; valued for their flavor, onions are low in nutrients.

The onion plant is potentially a biennial, producing large bulbs the first year and seed the next. Plants may be grown from seed, as transplants of seedlings, or as small bulbs produced from thickly planted seed; when replanted, these bulbs reach maturity quickly. Mature onions are usually dried before marketing. Major world producers include China, India, the United States, and the Soviet Union; in the United States, California produces the largest crop, much of which is reserved for dehydrated products.