Fall harvest: Onions

Onions come from storage all year round but most onions are harvested in late summer through the fall.



The onion (Allium cepa) (Latin 'cepa' = onion), also known as the bulb onion or common onion, is used as a vegetable and is the most widely cultivated species of the genus Allium. This genus also contains several other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion (A. fistulosum), the Egyptian onion (A. ×proliferum), and the Canada onion (A. canadense). The name "wild onion" is applied to a number of Allium species but A. cepa is exclusively known from cultivation and its wild original form is not known. The onion is most frequently a biennial or a perennial plant, but is usually treated as an annual and harvested in its first growing season.
The onion plant has a fan of hollow, bluish-green leaves and the bulb at the base of the plant begins to swell when a certain day-length is reached. In the autumn the foliage dies down and the outer layers of the bulb become dry and brittle. The crop is harvested and dried and the onions are ready for use or storage. The crop is prone to attack by a number of pests and diseases, particularly the onion fly, the onion eelworm and various fungi that cause rotting. Some varieties of A. cepa such as shallots and potato onions produce multiple bulbs.
Onions are cultivated and used around the world. As a foodstuff they are usually served cooked, as a vegetable or part of a prepared savoury dish, but can also be eaten raw or used to make pickles or chutneys. They are pungent when chopped and contain certain chemical substances which irritate the eyes. Onions contain phenolics and flavonoids that have potential anti-inflammatory, anti-cholesterol, anticancer and antioxidant properties.

Roots, leaves and developing bulb

The onion plant (Allium cepa) is unknown in the wild but has been grown and selectively bred in cultivation for at least 7,000 years. It is a biennial plant but is usually grown as an annual. Modern varieties typically grow to a height of 15 to 45 cm (6 to 18 in). The leaves are blueish-green and grow alternately in a flattened, fan-shaped swathe. They are fleshy, hollow and cylindrical, with one flattened side. They are at their broadest about a quarter of the way up beyond which they taper towards a blunt tip. The base of each leaf is a flattened, usually white sheath that grows out of a basal disc. From the underside of the disc, a bundle of fibrous roots extends for a short way into the soil. As the onion matures, food reserves begin to accumulate in the leaf bases and the bulb of the onion swells.
In the autumn the leaves die back and the outer scales of the bulb become dry and brittle, and this is the time at which the crop is normally harvested. If left in the soil over winter, the growing point in the middle of the bulb begins to develop in the spring. New leaves appear and a long, stout, hollow stem expands, topped by a bract protecting a developing inflorescence. The flower-head takes the form of a globular umbel of white flowers with parts in sixes. The seeds are glossy black and triangular in cross section.

Sauteeing onions

Onions are often chopped and used as an ingredient in various hearty warm dishes, and may also be used as a main ingredient in their own right, for example in French onion soup or onion chutney. They are very versatile and can be baked, boiled, braised, fried, roasted, sautéed or eaten raw in salads. Onions are also used as a thickening agent for curries providing bulk. Onions pickled in vinegar are eaten as a snack. These are often served as a side serving in pubs and fish and chip shops throughout the United Kingdom and Australia, often served with cheese and/or ale in the United Kingdom. In North America, sliced onions are battered and deep fried and served as onion rings.





Common onions are normally available in three colors: yellow, red, and white. Yellow onions, also called brown onions, are full-flavored and are the onions of choice for everyday use. Yellow onions turn a rich, dark brown when caramelized and give French onion soup its sweet flavor. The red onion is a good choice for fresh use when its color livens up the dish. It is also used in grilling and char-broiling. White onions are the traditional onions that are used in classic Mexican cuisine. They have a golden color when cooked and a particularly sweet flavor when sautéed.
While the large mature onion bulb is the onion most often eaten, onions can be eaten at immature stages. Young plants may be harvested before bulbing occurs and used whole as scallions. When an onion is harvested after bulbing has begun but the onion is not yet mature, the plants are sometimes referred to as summer onions.
Additionally, onions may be bred and grown to mature at smaller sizes. Depending on the mature size and the purpose for which the onion is used, these may be referred to as pearl, boiler, or pickler onions, but differ from true pearl onions which are a different species. Pearl and boiler onions may be cooked as a vegetable rather than as an ingredient and pickler onions are often preserved in vinegar as a long-lasting relish.
Onions are available in fresh, frozen, canned, caramelized, pickled and chopped forms. The dehydrated product is available as kibbled, sliced, rings, minced, chopped, granulated and powder forms. Onion powder is a spice widely used when the fresh ingredient is not available. It is made from finely ground, dehydrated onions, mainly the pungent varieties of bulb onions, and has a strong odor. Being dehydrated, it has a long shelf life and comes in several varieties: white, yellow and red.

Jar of pickled onions

Most onion cultivars are about 89% water, 4% sugar, 1% protein, 2% fibre and 0.1% fat. They contain vitamin C, vitamin B6, folic acid and numerous other nutrients in small amounts. They are low in fats and in sodium, and with an energy value of 166kJ (40 kcal) per 100 g (3.5 oz) serving, they can contribute their flavor to savory dishes without raising caloric content appreciably.
Onions contain chemical compounds such as phenolics and flavonoids that basic research shows to have potential anti-inflammatory, anti-cholesterol, anticancer and antioxidant properties.[medical citation needed] These include quercetin and its glycosides quercetin 3,4'-diglucoside and quercetin-4'-glucoside. There are considerable differences between different varieties in potential antioxidant content. Shallots have the highest level, six times the amount found in Vidalia onions, the variety with the smallest amount.
Some people suffer from allergic reactions after handling onions. Symptoms can include contact dermatitis, intense itching, rhinoconjunctivitis, blurred vision, bronchial asthma, sweating and anaphylaxis. There may be no allergic reaction in these individuals to the consumption of onions, perhaps because of the denaturing of the proteins involved during the cooking process.
While onions and other members of the genus Allium are commonly consumed by humans, they can be deadly for dogs, cats, guinea pigs, monkeys and other animals. The toxicity is caused by the sulfoxides present in raw and cooked onions which many animals are unable to digest. Ingestion results in anaemia caused by the distortion and rupture of red blood cells. Sick pets are sometimes fed with tinned baby foods and any that contain onion should be avoided. Nor is it good for pets to be fed onion-containing leftovers such as pizza, canned spaghetti, Chinese dishes and onion rings. The typical toxic doses are 5 g (0.2 oz) per kg (2.2 lb) bodyweight for cats and 15 to 30 g (0.5 to 1.1 oz) per kg for dogs.
In India, some sects do not eat onions as they believe them to be an aphrodisiac. Various schools of Buddhism also advise against the consumption of onions and garlic because they increase desire when eaten cooked and anger when eaten raw.