in the general sense can be used for any plant in the
genus Allium but used without qualifiers usually
means Allium cepa, also called the garden onion.
Onions (usually but not exclusively the bulbs) are edible
with a distinctive strong flavor and pungent odor which
is mellowed by cooking. They generally have a papery outer
skin over a fleshy, layered inner core. Used worldwide for
culinary purposes, they come in a wide variety of forms
and colors (but generally brown, white or purple).
The common brown onion
tends to have a very pungent odor, and it makes the eyes
water. Some varieties have more or less of the
eye-watering chemicals, which also makes them taste
milder. 'Spanish onions' (the large white onions with a
purple skin and purple flecks) are much milder than brown
onions, making them more suitable for raw use in salads.
Onions may be grown from
seed or very commonly from "sets". Onion sets
are produced by sowing seed very thickly one year,
resulting in stunted plants which 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.
Either planting method
may be used to produce spring onions or green onions,
which are just onions harvested while immature, although
"green onion" is also a common name for the welsh
onion, Allium fistulosum which never produces
dry bulbs and the 'Spring onions' used in Asian cooking
are an entirely different variety which never grows a full