Onions Horticulture Onions Onions are part of the lily family, Amaryllidaceae, and belong to the genus Allium. Alliums have bulbous, onion-scented roots. Garlic, chives, shallots, and leeks also belong to this genus as do the ornamental alliums grown for their purple flowers. The common garden onions are termed Allium cepa by botanists. Allium meaning garlic and cepa meaning onion in Latin.
Onions are a more complicated class than other vegetables.
There are five ways to classify them. Their use, flavor, color, shape of the bulb and day length. Onions grown for storage often have a darker color with thicker skins, a more pungent flavor, and are usable for many months of the year. Fresh onions have a flavor that is milder and sweeter with a lighter color and thin skin. The flavors of onions range from sweet to pungent.