The onion plant has been grown and selectively bred in cultivation for at least 7,000 years. Onions are part of the allium family - along with shallots, garlic and leeks.
Onion sets are available as white or red for spring planting and as white onions for autumn planting. (Onion Sets are grown by sowing onion seed thickly late in the summer. The plants are allowed to grow just until they start forming bulbs. These immature bulbs are dug, cured like regular onions, then held in temperature-controlled warehouses until spring, when they are sold as onion sets).