The leek is a vegetable, a cultivar of Allium ampeloprasum, the broadleaf wild leek (syn. Allium porrum). The edible part of the plant is a bundle of leaf sheaths that is sometimes erroneously called a stem or stalk. The genus Allium also contains the onion, garlic, shallot, scallion, chive,[1] and Chinese onion. Three closely related vegetables, elephant garlic, kurrat and Persian leek or tareh, are also cultivars of A. ampeloprasum, although different in their uses as food.[2]
Source: Wikipedia