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Onion

The onion (*Allium cepa*) is a cultivated plant grown mainly for its edible bulb, which is widely used as a flavouring vegetable.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

The onion (Allium cepa) is a cultivated plant grown mainly for its edible bulb, which is widely used as a flavouring vegetable. It is a biennial plant in the amaryllis family that is usually grown as an annual and is cultivated around the world, especially in temperate regions. Onions are a common cool-season vegetable grown in Canadian gardens and agriculture, and they are widely used in Canadian cooking.

Description

The onion is a bulb-forming plant with hollow leaves and a short stem at the base of the bulb. Its edible bulb is made of concentric fleshy leaf bases and is valued for its pungent flavour.

Cultivation and distribution

Onions have been cultivated for thousands of years and are grown globally today. Sources identify southwestern or central Asia and Persia as likely origins, with later spread into many regions and large-scale production in countries such as China, India, and the United States.

Uses

The bulb is the most commonly eaten part, but the stems and leaves are also edible. Onions are used raw, cooked, dried, dehydrated, boiled, or pickled, and they are a major flavouring ingredient in many cuisines.

Varieties and forms

Onions include different colour and size types, such as white, red, yellow, Spanish, and Bermuda onions. Some related forms, such as scallions or bunching onions, are grown for their leaves rather than enlarged bulbs.

Key facts

  • The onion is one of the most widely cultivated species in the genus Allium.
  • It is grown primarily for its edible bulb, which is commonly eaten cooked but can also be eaten fresh.
  • Onions are usually grown as annual crops even though the plant is naturally biennial.
  • The plant is likely native to southwestern Asia and is now grown worldwide.
  • Onions are used in cooking in many forms, including soups, stews, salads, roasting, pickling, and frying.
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Canadian context

Onions are a common cool-season vegetable grown in Canadian gardens and agriculture, and they are widely used in Canadian cooking.

Frequently asked questions

What is the scientific name of the onion?
The scientific name is Allium cepa.
What family does the onion belong to?
It belongs to the amaryllis family, Amaryllidaceae.
Which part of the onion is eaten?
The bulb is the main edible part, though the leaves and stems are also edible.
Where did onions originate?
They are likely native to southwestern Asia, with some sources also pointing to central Asia or Persia as origin areas.
Are onions annual or biennial plants?
Onions are naturally biennial, but they are usually cultivated as annuals.
How are onions used in food?
They are used raw or cooked in dishes such as soups, stews, salads, roasts, and pickles.

References

  1. Wikipediahttps://www.wikiwand.com/en/articles/Onion
    Supports: Scientific name, genus, and status as a widely cultivated Allium species.
  2. Encyclopaedia Britannicahttps://www.britannica.com/plant/onion-plant
    Supports: Description, family, likely native range, cultivation, and culinary uses.
  3. Penn State PlantVillagehttps://plantvillage.psu.edu/topics/onion/infos
    Supports: Edible bulb, leaves and stems, and common uses.
  4. Britannica Kidshttps://kids.britannica.com/students/article/onion/276190
    Supports: Plant description, edible bulb, origin, and production regions.
  5. New Mexico State Universityhttps://onion.nmsu.edu/resources/facts.html
    Supports: Origin area, cultivation history, and family-related facts.
  6. University of California Agriculture and Natural Resourceshttps://ucanr.edu/sites/default/files/2010-09/52157.pdf
    Supports: Onions as a cool-season biennial plant usually grown as an annual.
  7. University of Connecticuthttps://homegarden.cahnr.uconn.edu/factsheets/onions/
    Supports: Genus relationships, cultivation, and long history of cultivation.
  8. North Carolina State Universityhttps://plants.ces.ncsu.edu/plants/allium-cepa/
    Supports: Family placement, edible bulbs and tops, and origin notes.