Editing Onion (section)

== Description ==

The onion is a [[biennial plant]] but is usually grown as an annual. Modern varieties typically grow to a height of {{convert|15|to|45|cm|0|abbr=on}}. The leaves are yellowish- to bluish green and grow alternately in a flattened, fan-shaped swathe. They are fleshy, hollow, and cylindrical, with one flattened side. They are at their broadest about a quarter of the way up, beyond which they taper to blunt tips. The base of each leaf is a flattened, usually white sheath that grows out of the basal plate of a bulb. From the underside of the plate, a bundle of [[Fibrous root system|fibrous roots]] extends for a short way into the soil. As the onion matures, food reserves accumulate in the leaf bases, and the bulb of the onion swells.<ref name=RHS/>

In the autumn, the leaves die back, and the outer scales of the bulb become dry and brittle, so the crop is normally harvested. If left in the soil over winter, the growing point in the middle of the bulb begins to develop in the spring. New leaves appear, and a long, stout, hollow stem expands, topped by a [[bract]] protecting a developing inflorescence. The [[wikt:inflorescence|inflorescence]] takes the form of a rounded [[wikt:umbel|umbel]] of white flowers with parts in sixes. The seeds are glossy black and triangular in cross-section.<ref name=RHS /> The average pH of an onion is around 5.5.<ref>{{Cite web |url=https://foodsafety.wisc.edu/business_food/files/Approximate_pH.pdf |title=Approximate pH Values of Common Foods and Ingredients |website=Wisconsin Food Safety and Health |archive-url=https://web.archive.org/web/20121224184605/http://www.foodsafety.wisc.edu/business_food/files/Approximate_pH.pdf |archive-date=2012-12-24 |url-status=dead |access-date=8 January 2018}}</ref>

<gallery class=center mode=nolines widths=180 heights=180>
File:ARS red onion.jpg|Roots, leaves and developing bulb
File:Onion Flower Bangladesh.jpg|Inflorescence with flower buds
File:Onion seed.jpg|Seeds
</gallery>