(Allium sp.– Family Liliaceae [formerly Amaryllidaceae])
However, the vast majority of the vegetables comes from one genus, Allium, the onion. Varieties of Allium cepa fall into several differnt groups according to their colour, shape, and use.
Basically, onions fall into the following classifications:
includes all common western round or globe onions with single bulbs which, in their immature state, are used as spring onions; the aggregate onions with multiple underground bulbs as shallots, the every ready, and potato onions; also the tree onions known as the Egyptian or top-set onions which reproduce by forming miniature self-planting bulbs on top of the stem. Both of the last two groups are multiplier onions.
is the most important in oriental countries. Although known as the Welsh onion, it has nothing to do with Wales. In North America, it is called a scallion and likely to mean green shallots. Hybrids of these last two species account for most of the hundreds of onion varieties and cultivars.
is the Chinese jiao tou and the Japanese rakkyo, oriental pickling onions.
A porrum is the leek, but also includes a variety called the bunching pear onion.
is a species which fills the role of leek in the Near and Middle East.
is the species usually called rocambole.
A. sativum is garlic.
A. ampeloprasum is the wild ancestor of the leek and a species which exists in many forms. One of them is the elephant garlic.
A ursinum is the wild garlic or ramsons.
More onions are consumed than any other vegetable. Over 6,000 years ago, the onion was already one of the most important vegetable and medicinal plants of Central Asia, present day Pakistan, Northwest India, and the Mediterranean.
It is one of the oldest of all cultivated plants and now grows in many different forms and in almost every area of the world, but chiefly in the warmer subtropics and the temperate zones. The major world producers are the US, China, Russia, India, Turkey, and Spain.
It is assumed that the onion is native to Central Asia since the first written records of it came from there. However, no seed or tissue has ever been found fossilized.
Onions were used by the Egyptians, not only as food, but also as a preservative during mummification when they were placed in the thorax, pelvis, and near the eyes.
Pliny the Elder (23-79 CE) recorded six varieties in ancient Rome, where they had developed varieties with varying flavours. There is no record that the ancient Greeks used them as decorative or symbolic motifs, but Olympic athletes did use them before games to “purify and condition their blood”. Greek and Phoenician sailors carried onion, and it is now thought that their vitamin C content helped to prevent scurvy.
Onions contain about 8% sugar in the form of glucose and saccharose and up to 90% water. They also contain protein, calcium, sulfur, fluoride, provitamin A, B complex vitamins, and vitamins C and E; and have long been used for medicinal purposes. We now know that there are more than 100 sulfur compounds in onions that have anti-inflammatory effects. However, many are known to change readily when heated or are broken down after cutting. As with garlic, onions also contain the volatile, natural antibiotic oil called allicin, responsible for its pungent flavour.
European, Asian, and Native American medicines are filled with onion treatments. Some of them include cough relief during colds and their use as poultices drawing poisons from wounds and ulcers. Even in relatively modern times, onion poultices are used on the soles of the feet to reduce high fevers or placed on the chest to relieve congestion.
One ancient remedy included onion tea to relieve cholera, fevers, and headaches, as well as being treatments for gout, arthritis, soothing burns, and speeding healing. Modern research is proving that eating onions and garlic reduces LDL (low density lipoprotein) or cholesterol, responsible for clogging the arteries.
These anti-clotting properties make them doubly helpful to the circulatory system. Onions have also been known to lower blood sugar levels, and they have readily demonstrated their antimicrobial properties.
Using garlic or onion pills does not have nearly the effect on the system as eating the fresh product. Since many of the beneficial properties have yet to be identified, they cannot be fully reproduced in any laboratory. Only the natural food itself can have the right combination of enzymes, sulfides, precursors, etc. that benefit human health.
Onions also have substances called saponins that fight against cancer. To put it simply, saponins help the cell DNA to stop producing bad cells and make only good ones.
Onions contain hundreds of various compounds that aid in better health, including those that prevent arterial buildup of fats that can cause heart attacks or strokes. These compounds also promote secretions in the upper respiratory tract that move along, carrying out harmful microbes in the process.
When these secretions are allowed to stagnate, microbes have the opportunity to multiply. Onions can help fight off bacteria, fungi, and viruses in the body. Chewing raw onion for at least three minutes is said to kill any bacteria in the mouth that might be causing toothaches or the gums to bleed.
Putting a slice of onion directly on an insect bite will cut down on the itching and prevent infection. Using warmed, raw onions as a poultice will draw out any foreign matter lodged in the skin. Poultices can also be used to draw out any inflammation or fevers. Onions also contain compounds that help with digestion.
When onions are cut, the cell walls are damaged, releasing a sulfur compound called propanethial-S-oxide that floats into the air. The chemical, identified in 1985 by researchers at the University of St. Louis in Missouri, turns into sulfuric acid when it comes into contact with water. This explains why it stings if it gets into the eyes or a cut; an effect which can be lessened by slicing fresh onions under cold running water, which technically, will dilute the sulfur compound before it can float up into the air.
Another way, is to chill the onion for an hour or so in the refrigerator before it is sliced. The cold temperatures slow the movement of the atoms in the sulfur compound so that it is not able to float up into the air to reach the eyes. Depending on the onion, some will have a high level of this pyruvate, while in others, it will be lower.
Onions should not be stored in the same area as potatoes as they will emit a gas that speeds up maturity, causing each to rot faster.
Storing onions on a rope enables the air to circulate around them reducing, the possibility of diseases and molds. It is also attractive and a convenient storing method.
In order to plait a bunch, firmly tie two onions at the base then wind the leaves of each onion firmly around the string with each bulb barely resting on the onion below. When the top of the string is reached, tie a firm knot around the top and then hang to dry. As onions are needed, they can be cut from the rope.
With all its powerful aroma, the onion is not immune to pests. The onion fly larvae
can tunnel into the bulbs, causing the stems to wilt and become yellow. Seedlings and small plants are most susceptible and usually die.
Crop rotation is advised to avoid this and other problems, rather than applying insecticides. Removal of affected onions from the area is also advised, but they should not to be put into the compost pile.
When attacked by stem eelworm, bulbs become distorted, crack, soften, and then die. Should this happen, dispose of plant debris and affected plants, then rotate the crops. Companion planting is another solution and planting parsley is said to keep onion flies away.
are very small white or yellow onions and reach about two inches in diameter. They are left whole in soups and stews.
Bulb onions are perennials cultivated as biennials and normally seed in their second year. These include the pungent storage onions (yellow, white, and red), sweet onions, pearl onions, boiling onions, and the flat small onions (cipolline) that Italians use for pickling. Bulb onions may have brown, red, white, or yellow skin; be round or elongated, spindle-shaped or flattened; and are encircled by several layers of dry skin. Sizes range from very small to over four inches in diameter. Grouped with the bulb onions are Japanese onions, a type of the perennial Allium fistulosum, which are grown as an annual for overwintering.
Creaming onions are fresh onions sold by the bunch. Each onion has a large, white bulb still attached to a green stalk. Usually, they are the yellow onions picked young, but can sometimes be overly mature green onions. Their crisp flavour is hotter than green onions.
Pearl onions are even smaller, about an inch thick. They have a thin, white wrapper and white flesh that is crisp and sweet. These are perfect for marinating or pickling. There is also a Pink Pearl variety.
are an Italian specialty. Their thin, red to purple skin and mild flesh make them especially popular as a decorative salad onion. Like Spanish onions, they are sweet and mild, but have a thicker, coarser texture than the Spanish. These onions make a colourful addition to any salad, but their colour can bleed into other ingredients if sautéed with them. The red Semian onion is a popular variety in Italy. It has an unusually elongated, narrow shape, and can grow to be a foot in length.
Sweet onions are mild, juicy, crisp onions that can be eaten raw. They are relatively low in sulfur, making their flavour very mild. Since their water content is about 85%, they are juicy. However, because of these traits, their storage capacity is limited to just a couple of months. Growers use expensive atmosphere-controlled coolers to extend their market season, but home gardeners must consider them seasonal and perishable. A sweet onion generally weighs about half a pound. The best known ones are Vidalia, from Georgia, USA; the Texas 1015 Supersweet; Mauis from Hawaii; Walla Walla from Washington State; Arizona; California Imperial; and one from Ontario, Canada, called the Norfolk. Sweetened Sandwich is a long-day hybrid that actually sweetens in storage, but its pungency also increases. Long term varieties include Blanco Duro, Stuttgarten, Ebenezer, Red Creole, Yellow Tongue, and Yula.
White storage onions
can weigh more than a pound each, but their keeping quality is not as long as that of the yellow onion. The white onions have a white papery wrap and a slightly sharper, cleaner flavour, and are used extensively in Mexican cooking. They are also prized in Italy and Spain for their sweet flavour, which can vary from mild to strong, depending on the variety.
Yellow storage onions
are the same as the common cooking onions. They can be as small as an apricot or as large as an orange. They can be round or oval with a heavy brown wrapper. They are hot if eaten raw, but the heat dissipates during cooking. Spanish or Bermuda onions are actually very large yellow onions. Because of their high water content, they are sweeter and milder than the common yellow onions. Red or yellow onions have a bioflavonoid called quercetin, but white onions do not.
Albion is a medium sized round onion with a white bulb.
is a large variety, round and straw-coloured with a mild flavour.
Buffalo is a high-yielding onion sown in the summer and harvested the following year. It has round firm bulbs with a good flavour.
Express Yellow O-X is a Japanese onion sown in the summer and harvested the following year.
is a large round onion with mild-tasting flesh, but it does not store well.
Marshalls Giant Red Fen Globe
is an old heavy cropping variety with a mild flavour.
is a beautiful dark red-skinned onion with a strong flavour.
is large, pale yellow, round, and an excellent keeper.
Senshyu Semi-Globe Yellow
is a Japanese onion with deep yellow skin.
is an old high-yielding variety with straw-coloured skin and shows an excellent resistance from going to seed.
is a reliable variety with flattened bulbs and a mild flavour. It is a good keeper and slow to bolt.
Torpedo, or Red Italian,
is a spindle-shaped onion that is mild-flavoured, but does not store well.