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|species=cepa

|species=cepa

|common_name=Onion

|common_name=Onion

|features=edible

|features=edible

|Temp Metric=°F

|Temp Metric=°F

|image=Onions.jpg

|image=Onions.jpg

|image_width=240

|image_width=240

==Cultivation==

==Cultivation==

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Prefers a sunny sheltered position in a rich light well-drained soil[1, 16]. Prefers a pH of at least 6.5[200]. 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[200]. For best growth, however, cool weather is desirable at the early stages of growth[200]. Plants are frost-tolerant but prolonged temperatures below 10°c cause the bulb to flower[200]. Optimum growth takes place at temperatures between 20 and 25°c[200]. Bulb formation takes place in response to long-day conditions[200]. Plants are perennial but the cultivated forms often die after flowering in their second year though they can perennate by means of off-sets[1]. The onion was one of the first plants to be cultivated for food and medicine[244]. 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[200]. This species was derived in cultivation from A. oschaninii[203]. 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[18, 20, 54, 201]. This plant is a bad companion for alfalfa, each species negatively affecting the other[201]. Members of this genus are rarely if ever troubled by browsing deer[233].

===Propagation===

===Propagation===

[[File:Onion whitebackground.jpg|thumb|Onion growing shoots]]

[[File:Onion whitebackground.jpg|thumb|Onion growing shoots]]

Onions may be grown from seed or, more commonly today, from sets started from seed the previous year. Onion sets are produced by sowing seed very thickly one year, resulting in stunted plants that produce very small bulbs. These bulbs are very easy to set out and grow into mature bulbs the following year, but they have the reputation of producing a less durable bulb than onions grown directly from seed and thinned.

Onions may be grown from seed or, more commonly today, from sets started from seed the previous year. Onion sets are produced by sowing seed very thickly one year, resulting in stunted plants that produce very small bulbs. These bulbs are very easy to set out and grow into mature bulbs the following year, but they have the reputation of producing a less durable bulb than onions grown directly from seed and thinned.

*[[Welsh onion]] – Sometimes referred to as green onion or spring onion, although these onions may refer to any green onion stalk.

*[[Welsh onion]] – Sometimes referred to as green onion or spring onion, although these onions may refer to any green onion stalk.

*[[Leek]]

*[[Leek]]

*[[Yellow onion]] - generally tapered ends, brown skin over the onion, usually sold in 3&nbsp;lb bags of yellow webbed plastic.

*[[Yellow onion]] - generally tapered ends, brown skin over the onion, usually sold in 3 lb bags of yellow webbed plastic.

*[[Sweet onion]] - flatter ends and sold individually. Spanish and Vidalia

*[[Sweet onion]] - flatter ends and sold individually. Spanish and Vidalia

==References==

==References==

*[[Standard Cyclopedia of Horticulture]], by L. H. Bailey, MacMillan Co., 1963

*[[Standard Cyclopedia of Horticulture]], by L. H. Bailey, MacMillan Co., 1963

<!--- xxxxx  *Flora: The Gardener's Bible, by Sean Hogan. Global Book Publishing, 2003. ISBN 0881925381  -->

<!--- xxxxx  *Flora: The Gardener's Bible, by Sean Hogan. Global Book Publishing, 2003. ISBN 0881925381  -->

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