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, and Chinese onion. Three closely related vegetables, elephant garlic, kurrat and Persian leek or tareh.
Leek cultivars fall into two broad categories. The less hardy short-season leeks are planted in the spring for harvest during the summer and early fall. The hardier long-season (100 or more days to maturity) leeks are also planted in the spring in the north and late summer or fall in the south.
They can be harvested throughout the winter in mild climates and up until the ground freezes in northern areas. To develop the long, white stalks that are the part of the leek we use in cooking, plants need to be blanched, or have light excluded, by covering the stalks with soil as the plants grow.