Allium is a large genus of monocotyledonous flowering plants with around 1000 accepted species,[4][5] making Allium the largest genus in the family Amaryllidaceae and amongst the largest plant genera in the world.[6] Many of the species are edible, and some have a long history of cultivation and human consumption as a vegetable including the onion, garlic, scallions, shallots, leeks, and chives, with onions being the second most grown vegetable globally after tomatoes as of 2023.[7][8]
Allium species occur in temperate climates of the Northern Hemisphere, except for a few species occurring in Chile (such as A. juncifolium), Brazil (A. sellovianum), and tropical Africa (A. spathaceum). They vary in height between 5–150 centimetres (2–59 in). The flowers form an umbel 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.
Various Allium species have been cultivated from the earliest times. About a dozen species are economically important as crops, or garden vegetables, and an increasing number of species are important as ornamental plants.[15][16] Plants of the genus produce chemical compounds, mostly derived from cysteinesulfoxides, that give them a characteristic onion or garlic taste and odor.[15] Many are used as food plants, though not all members of the genus are equally flavorful. In most cases, both bulb and leaves are edible. The characteristic Allium flavor depends on the sulfate content of the soil the plant grows in.[15] In the rare occurrence of sulfur-free growth conditions, all Allium species completely lose their usual pungency.
^Cite error: The named reference Linnaeus was invoked but never defined (see the help page).
^Knud Rahn. 1998. "Alliaceae" pages 70-78. In: Klaus Kubitzki (editor). The Families and Genera of Vascular Plants volume III. Springer-Verlag: Berlin;Heidelberg, Germany. ISBN978-3-540-64060-8