This article is about the plant. For other uses, see Onion (disambiguation).
"Onions" redirects here. For the surname, see Onions (surname).
Onion
A display of commercially-grown bulbs, including red and yellow cultivars.
Scientific classification
Kingdom:
Plantae
Clade:
Tracheophytes
Clade:
Angiosperms
Clade:
Monocots
Order:
Asparagales
Family:
Amaryllidaceae
Subfamily:
Allioideae
Genus:
Allium
Subgenus:
A. subg. Cepa
Species:
A. cepa
Binomial name
Allium cepa
L.
Synonyms[1]
Species synonymy
Allium angolense Baker
Allium aobanum Araki
Allium ascalonicum auct.
Allium ascalonicum var. condensum Millán
Allium ascalonicum var. fertile Millán
Allium ascalonicum f. rotterianum Voss ex J.Becker
Allium ascalonicum var. sterile Millán
Allium cepa var. aggregatum G.Don
Allium cepa var. anglicum Alef.
Allium cepa var. argenteum Alef.
Allium cepa var. bifolium Alef.
Allium cepa var. crinides Alef.
Allium cepa var. flandricum Alef.
Allium cepa var. globosum Alef.
Allium cepa var. hispanicum Alef.
Allium cepa var. jamesii Alef.
Allium cepa var. lisboanum Alef.
Allium cepa var. luteum Alef.
Allium cepa var. multiplicans L.H.Bailey
Allium cepa var. portanum Alef.
Allium cepa var. praecox Alef.
Allium cepa var. rosum Alef.
Allium cepa var. sanguineum Alef.
Allium cepa var. solaninum Alef.
Allium cepa var. tripolitanum Alef.
Allium cepa var. viviparum (Metzg.) Alef.
Allium cepaeum St.-Lag.
Allium commune Noronha
Allium cumaria Buch.-Ham. ex Wall.
Allium esculentum Salisb.
Allium napus Pall. ex Kunth
Allium nigritanum A.Chev.
Allium pauciflorum Willd. ex Ledeb.
Allium salota Dostál
Ascalonicum sativum P.Renault
Cepa alba P.Renault
Cepa esculenta Gray
Cepa pallens P.Renault
Cepa rubra P.Renault
Cepa vulgaris Garsault
Kepa esculenta Raf.
Porrum cepa (L.) Rchb.
An onion (Allium cepa L., from Latin cepa meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus Allium. The shallot is a botanical variety of the onion which was classified as a separate species until 2011.[2][3]: 21 Its close relatives include garlic, scallion, leek, and chive.[4]
This genus also contains several other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion Allium fistulosum, the tree onion Allium × proliferum, and the Canada onion Allium canadense. The name wild onion is applied to a number of Allium species, but A. cepa is exclusively known from cultivation. Its ancestral wild original form is not known, although escapes from cultivation have become established in some regions.[5] 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 its bulb at the base of the plant begins to swell when a certain day-length is reached. The bulbs are composed of shortened, compressed, underground stems surrounded by fleshy modified scale (leaves) that envelop a central bud at the tip of the stem. In the autumn (or in spring, in the case of overwintering onions), the foliage dies down and the outer layers of the bulb become more 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 which can 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 food item, they are usually served raw,[citation needed] as a vegetable or part of a prepared savoury dish, but can also be eaten cooked or used to make pickles or chutneys. They are pungent when chopped and contain certain chemical substances which may irritate the eyes.
^"Allium cepa L.". World Checklist of Selected Plant Families. Royal Botanic Gardens, Kew – via The Plant List. Note that this website has been superseded by World Flora Online
^"Allium cepa". Germplasm Resources Information Network. Agricultural Research Service, United States Department of Agriculture. Retrieved 20 August 2010.
^Fritsch, Reinhard M.; Friesen, Nikolai (2002). "Chapter 1: Evolution, Domestication, and Taxonomy". In Rabinowitch, Haim D.; Currah, Lesley (eds.). Allium Crop Science: Recent Advances. Wallingford, UK: CABI Publishing. doi:10.1079/9780851995106.0005. ISBN 0-85199-510-1. OCLC 228168061. S2CID 189956991.
^Block, E. (2010). Garlic and Other Alliums: The Lore and the Science. Royal Society of Chemistry. ISBN 978-0-85404-190-9. Archived from the original on 1 August 2020. Retrieved 30 June 2020.
^McNeal, Dale W. Jr.; Jacobsen, T. D. (2002). "Allium cepa". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 26. New York and Oxford: Oxford University Press – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
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