Allium species comprise around 1000 flowering plants that includes the cultivated onion, garlic, shallot, leek, and chives. Carl Linnaeus first described the genus Allium in 1753. Some sources refer to Greek ἀλέω (aleo, which means to avoid) by reason of the smell of garlic. Various Alliums have been cultivated from the earliest times, and about a dozen species are economically important crops.
Allium species occur in temperate climates of the Northern Hemisphere, except for a few species occurring in South-America and Africa.
Alliums vary in height between just a few cm and up to 2 meters. The flowers form an umbel at the top of a leafless stalk. The bulbs vary in size between species, from small (around 2 mm in diameter) to fairly large (10–12 cm). Some species develop thickened leaf bases or roots instead of bulbs. Most Allium plants produce chemical compounds derived from the amino acid cysteine, that give them a characteristic taste and odor. In most cases, both bulbs and leaves are edible.
Many Allium species and hybrids are cultivated as ornamentals that produce spherical umbels in a wide variety of sizes and colors.
Many varieties or cultivars are vegetatively multiplied selections of true species. The breeding of hybrids on the other hand is a more formidable task taking many years by first setting up inter-species crossings, thereafter harvesting and sowing the seeds, then growing the seedlings to mature flowering plants (which may take up to 6 years), followed by careful selection of a single plant and several years of vegetative multiplication.