Mixed onions.jpg
Scientific classification edit
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Asparagales
Family: Amaryllidaceae
Subfamily: Allioideae
Genus: Allium
A. cepa
Binomial name
Allium cepa
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.

The onion (Allium cepa L., from Latin cepa "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus Allium. Its close relatives include the garlic, scallion, shallot, leek, chive,[2] and Chinese onion.[3]

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 (A. ×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.[4] 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 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 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.

  1. ^ "Allium cepa L.". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew – via The Plant List.
  2. ^ Block, E. (2010). Garlic and Other Alliums: The Lore and the Science. Royal Society of Chemistry. ISBN 978-0-85404-190-9.
  3. ^ "AllergyNet — Allergy Advisor Find". Allallergy.net. Archived from the original on 15 June 2010. Retrieved 14 April 2010.
  4. ^ McNeal Jr., Dale W.; Jacobsen, T. D. (2002). "Allium cepa". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). 26. New York and Oxford – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.

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