Onion is a term used for many plants in the genus Allium. They are known by the common name "onion" but, used without qualifiers, it usually refers to Allium cepa. Allium cepa is also known as the "garden onion" or "bulb" onion. It is grown underground by the plant as a vertical shoot that's used for food storage, leading to the possibility of confusion with a tuber, which it's not. Allium cepa is known only in cultivation, but related wild species occur in Central Asia. The most closely relat… (More on Onions)