Onion, Garden onion
Allium cepa

Family: Alliaceae

What it is like

Allium cepa is an evergreen Bulb growing to 0.6 m (2ft). See above for USDA hardiness. It is hardy to UK zone 5 and is not frost tender. It is in flower from June to July. The species is hermaphrodite (has both male and female organs) and is pollinated by Bees, insects. Suitable for: light (sandy) and medium (loamy) soils and prefers well-drained soil. Suitable pH: mildly acid, neutral and basic (mildly alkaline) soils and can grow in very alkaline soils. It cannot grow in the shade. It prefers moist soil.

Height (m): 0.6

Where it is found

Not known in the wild.

W. Asia - Iran? The original habitat is obscure.

Conservation Status:

Countries/locations it is found in

How it is used

Food

Rating: 5

Bulb - raw or cooked. A very versatile food, the bulb can be 10cm or more in diameter and is widely used in most countries of the world. Eaten raw, it can be sliced up and used in salads, sandwich fillings etc, it can be baked or boiled as a vegetable in its own right and is also commonly used as a flavouring in soups, stews and many other cooked dishes. Some cultivars have been selected for their smaller and often hotter bulbs and these are used for making pickles. Leaves - raw or cooked. There are some cultivars, the spring onions, that have been selected for their leaves and are used in salads whilst still young and actively growing - the bulb is much smaller than in other cultivars and is usually eaten with the leaves. By successional sowing, they can be available at any time of the year. Flowers - raw. Used as a garnish on salads. The flowers are somewhat dry and are less pleasant than many other species. The seeds are sprouted and eaten. They have a delicious onion flavour.

Root: includes bulbs, corms, tubers, rhizomes etc.

Seed: includes nuts, cereals, peas and beans.

Medicine

Rating: 3

Although rarely used specifically as a medicinal herb, the onion has a wide range of beneficial actions on the body and when eaten (especially raw) on a regular basis will promote the general health of the body. The bulb is anthelmintic, anti-inflammatory, antiseptic, antispasmodic, carminative, diuretic, expectorant, febrifuge, hypoglycaemic, hypotensive, lithontripic, stomachic and tonic. When used regularly in the diet it offsets tendencies towards angina, arteriosclerosis and heart attack. It is also useful in preventing oral infection and tooth decay. Baked onions can be used as a poultice to remove pus from sores. Fresh onion juice is a very useful first aid treatment for bee and wasp stings, bites, grazes or fungal skin complaints. When warmed the juice can be dropped into the ear to treat earache. It also aids the formation of scar tissue on wounds, thus speeding up the healing process, and has been used as a cosmetic to remove freckles. Bulbs of red cultivars are harvested when mature in the summer and used to make a homeopathic remedy. This is used particularly in the treatment of people whose symptoms include running eyes and nose. The German Commission E Monographs, a therapeutic guide to herbal medicine, approve Allium cepa Onion for appetite loss, arteriosclerosis, dyspeptic complaints, fevers & colds, cough/bronchitis, hypertension, tendency to infection, inflammation of mouth and pharynx, common cold.

Anthelmintic: Expels parasites from the gut.

Antiinflammatory: Reduces inflammation of joints, injuries etc.

Antiseptic: Preventing sepsis, decay or putrefaction, it destroys or arrests the growth of micro-organisms.

Antispasmodic: Relaxes muscular spasms and cramps, calming nervous irritation.

Appetizer: Improves the appetite

Carminative: Reduces flatulence and expels gas from the intestines.

Diuretic: Acts on the kidneys, promoting the flow of urine.

Expectorant: Clears phlegm from the chest by inducing coughing.

Febrifuge: Reduces fevers.

Homeopathy: A plant used in homeopathic treatments.

Hypoglycaemic: Reduces the levels of sugar in the blood.

Hypotensive: Reduces blood pressure, it is used in the treatment of high blood pressure

Lithontripic: Removes stones from the kidney, bladder etc.

Skin: Plants used in miscellaneous treatments for the skin.

Stings: Used in the treatment of stings and insect bites.

Stomachic: Aids and improves the action of the stomach.

Tonic: Improves general health. Slower acting than a stimulant, it brings steady improvement.

Other

Rating: 3

The juice of the plant is used as a moth repellent and can also be rubbed onto the skin to repel insects. The plant juice can be used as a rust preventative on metals and as a polish for copper and glass. A yellow-brown dye is obtained from the skins of the bulbs. Onion juice rubbed into the skin is said to promote the growth of hair and to be a remedy for baldness. It is also used as a cosmetic to get rid of freckles. The growing plant is said to repel insects and moles. A spray made by pouring enough boiling water to cover 1kg of chopped unpeeled onions is said to increase the resistance of other plants to diseases and parasites.

Cosmetic: Used to improve the physical appearence of a person.

Dye: Plants that provide dyes.

Hair: Plants used as hair shampoos, tonics, to treat balding etc.

Polish: Plants used to give a shine to metals, wood etc.

Repellent: Plants that are said to deter but not necessarily kill various mammals, birds, insects etc.

Rust: Plants that can be used to prevent or treat rust.

How it is grown

Prefers a sunny sheltered position in a rich light well-drained soil. Prefers a pH of at least 6.5. Plants tolerate a pH in the range of 4.5 to 8.3. Onions are best grown in a Mediterranean climate, the hot dry summers ensuring that the bulbs are ripened fully. For best growth, however, cool weather is desirable at the early stages of growth. Plants are frost-tolerant but prolonged temperatures below 10°c cause the bulb to flower. Optimum growth takes place at temperatures between 20 and 25°c. Bulb formation takes place in response to long-day conditions. Plants are perennial but the cultivated forms often die after flowering in their second year though they can perennate by means of off-sets. The onion was one of the first plants to be cultivated for food and medicine. It is very widely cultivated in most parts of the world for its edible bulb and leaves, there are many named varieties capable of supplying bulbs all the year round. This species was derived in cultivation from A. oschaninii. Most forms are grown mainly for their edible bulbs but a number of varieties, the spring onions and everlasting onions, have been selected for their edible leaves. There are several sub-species: Allium cepa 'Perutile' is the everlasting onion with a growth habit similar to chives, it is usually evergreen and can supply fresh leaves all winter. Allium cepa aggregatum includes the shallot and the potato onion. These are true perennials, the bulb growing at or just below the surface of the ground and increasing by division. Plants can be divided annually when they die down in the summer to provide bulbs for eating and propagation. Allium cepa proliferum is the tree onion, it produces bulbils instead of flowers in the inflorescence. These bulbils have a nice strong onion flavour and can be used raw, cooked or pickled. Onions grow well with most plants, especially roses, carrots, beet and chamomile, but they inhibit the growth of legumes. This plant is a bad companion for alfalfa, each species negatively affecting the other. Members of this genus are rarely if ever troubled by browsing deer.

Propagating it: Seed. Early sowings can be made in February in a greenhouse to be planted out in late spring. The main sowing is made in March or April in an outdoor seedbed, this bed must be very well prepared. A sowing can also be made in an outdoor seedbed in August of winter hardy varieties (the Japanese onions are very popular for this). These overwinter and provide an early crop of onion bulbs in June of the following year. Onion sets can be planted in March or April. Sets are produced by sowing seed rather thickly in an outdoor seedbed in May or June. The soil should not be too rich and the seedlings will not grow very large in their first year. The plants will produce a small bulb about 1 - 2cm in diameter, this is harvested in late summer, stored in a cool frost-free place over winter and then planted out in April. A proportion of the bulbs will run quickly to seed but most should grow on to produce good sized bulbs.

Best place to grow: Cultivated Beds;

Habit: Bulb

Hardiness: 4-10

Growth:

Soil: Light (sandy), medium

Shade: No shade

Moisture: Moist

Things to keep in mind

There have been cases of poisoning caused by the consumption, in large quantities and by some mammals, of this plant. Dogs seem to be particularly susceptible. Hand eczema may occur with frequent handling. May interfere with drug control of blood sugar .

Its other names

Local names

Synonyms

Allium angolense, Allium aobanum, Allium ascalonicum, Cepa esculenta