The onion is a plant with a large bulb at its base. It can grow for many years, but is normally harvested in its first year. It has a very distinctive smell.

Like most bulb plants, in the wild, onions begin to swell up and produce shoots when days reach a certain length. It then sends up tall flower stems which carry white flowers. By autumn the leaves die down again.

When they are used as a crop, onions are harvested in early Autumn and hung up to dry. They store well in dry air.

Onions are believed to have substances in them that may reduce inflammation, as well as anti-cholesterol, anticancer and antioxidant properties.