onion

A Cornish onion grower with some of his produce. Onions are sensitive to the number of daylight hours during the growing season. By this measure they can be separated into three kinds: long-day, mid-day, and short-day. The amount of daylight they receive during the British summer favours the growing of long-day onions.

Plant belonging to the lily family, whose bulb has a strong, distinctive smell and taste. Cultivated from ancient times, it may have originated in Asia. The bulb is edible; its pale concentric layers of leaf bases contain an oil that is released into the air when the onion is cut open, causing the eyes to water. Onions are used extensively in cooking. (Allium cepa, family Liliaceae.)

The onion is a biennial plant, the common variety producing a bulb in the first season and seeds in the second.