onion
Edible bulbs of plants, onions are low in nutrients but highly valued for their flavor. They are widely used throughout the world in a variety of foods and may be cooked, pickled, or eaten raw. Onions are also known for their medicinal powers. They have been used to cure everything from colds and earaches to animal bites and warts. Onions belong to the lily family and are related to leeks, garlic, and chives.
Among the oldest known crops, onions have been grown by people for at least 5,000 years. They are probably native to southwestern Asia. Today onions are grown in mild climates around the world. Chief onion producers include China, India, the United States, and Turkey.
The common onion grows on a plant that has one or more leaf stalks. These stalks can reach a height of 21/2 to 6 feet (0.8 to 1.8 meters). At the top of the stalks are clusters of small greenish white flowers. The bulb forms at the bottom of the stalk, just under the soil. It is made up of many crisp, fleshy leaves. These leaves store food for the plant's growth.
Onion bulbs vary in size, shape, color, and sweetness. They range from less than 1 inch (2.5 centimeters) to more than 41/2 inches (11 centimeters) across and are typically round or squat. They may be white, yellow, or red. Large Spanish onions are the sweetest and juiciest. Red and white varieties are often milder than yellow onions.
Cutting onions often brings tears to a person's eyes. This tearing is caused by an oil in onions that is rich in the chemical element called sulfur. This oil is released into the air when onions are cut. When it mixes with fluid in the eyes, it leads to irritation and tearing.
It generally takes two years for an onion to grow from seed to a flowering plant. The onion develops a bulb in the first year and flowers in the second year. Onion plants that go through a series of alternating cold and warm spells, however, may flower in the first year and not fully develop their bulbs. Farmers grow onions from seed, planting in the fall. They harvest the bulbs the following summer. Home gardeners typically plant pencil-thin starter bulbs in the spring and harvest the bulbs a few months later.
Onion bulbs are ready to be harvested when the green tops of the plants fall over and start to turn brown. They are pulled and allowed to dry in the field for a few days. As they dry, they develop their characteristic brittle and paper-thin outer skin. Afterward the roots and withered tops are removed by hand or machine. Young onions, known as scallions, green onions, or spring onions, are harvested before the bulb fully develops.
Dried onions and onion juice are used as flavorings in many processed foods. Onion sprouts, grown from seeds, add spicy flavor and texture to salads and sandwiches. Scallions have a milder flavor than fully grown onion bulbs. They are often used fresh in salads and other foods. The green tops of scallions are a popular garnish.
