Leeks are another member of the Allium family, making it a relative of onions, scallions and even lilies. Leeks can be harvested early in the season (as smaller "summer leeks") or later for longer storage and a larger plant. Instead of developing a round bulb like an onion, leeks remain cylindrical with white/light green lower parts and green or blue-green leaves.
Store leeks in a plastic bag in the fridge. They will last a few weeks. The edible portion of leeks are the lower white/light green base. Be sure to wash out soil from between leaf layers. You can do this easily by cutting it once length-wise and running it under water before chopping it into pieces. Leeks are sort of like a creamier onion flavor in dishes and are great in egg dishes, soups, stews, sautees and finely chopped raw on salads.