Onion

Onion, common name for any of a genus of biennial herbs, of the lily family, native to Asia but cultivated in temperate and subtropical regions for thousands of years. The true onion is a bulb-bearing plant. Its long, hollow leaves with thickened bases make up most of the bulb. The white or pink flowers, which are borne in umbels, have six sepals, six petals, six stamens, and a solitary pistil. In the varieties known as top onions, the flowers are supplanted by bulblets, which may be grown to obtain new plants. The plant contains sulfurous, volatile oils that give it a characteristic pungent taste; one component readily dissolves in water to produce sulfuric acid, which may be produced in the eyes and induce tears.

Onions are one of the most versatile vegetables. They are eaten raw in salads, are cooked or pickled in a variety of ways, and are used as a flavoring or seasoning. Dehydrated onion products provide popular flavorings for soups and stews. Scientific studies indicate that onions are rich in antioxidants, which confer a range of health benefits.

Onions raised in warm areas are planted as winter crops and are milder in taste and odor than onions planted during the summer in cooler regions. Yellow Bermuda and white Spanish onions are among the mildest cultivated onions.

Onions are easily grown from seed that may be either field-grown directly or planted in beds to produce small bulbs, or sets. These are commonly dried and shipped to gardeners and commercial growers. Onions are adaptable to temperature and can be planted year-round as long as the soil is rich and moist. They are sown four to six weeks before the last frost in the spring or are planted in late summer for a fall crop.

The crop is allowed to ripen in the field until tops begin to bend and break. The bulbs are then pulled up and spread or hung in a dry area to cure. Once dry, they are normally stored and shipped in slotted or open-mesh bags to keep them dry enough to prevent sprouting.

Other onions in the genus include the nodding wild onion, the shallot, the chive, and the green onion, or common leek. Both the shallot and the green onion, which have small bulbs, are also known as scallions.

Scientific classification: Onions make up the genus Allium, of the family Liliaceae. The true onion is classified as Allium cepa; the nodding wild onion as Allium cernuum; the shallot as Allium ascalonicum; the chive as Allium schoenoprasum; and the green onion, or common leek, as Allium ampeloprasum.

See also Crop Farming; Garlic.