at the top of a leafless stalk. The bulbs vary in size between species, from small (around 2-3 mm in diameter) to rather large (8-10 cm). Some species (such as Welsh onion ''A. fistulosum'' and leeks (A. ampeloprasum)) develop thickened leaf-bases rather than forming bulbs as such.

Carl Linnaeus first described the genus Allium in 1753. The generic name