Leeks are members of the onion family and include several varieties, such as large American flag, King Richard and jolant. No matter which kind of leeks you have, they can be stored in a similar manner and for several months after purchasing or harvesting.
Store leeks during the winter while they're still in the garden. Cover the planting sites with more soil and several inches of mulch. If you live in an extremely cold area, you will have to harvest them for storage.
Store your harvested leeks at 32 degrees Fahrenheit in high humidity (95 to 100 percent). Alternatively, you can bury leeks in cold (32 to 40 degrees Fahrenheit), wet sand. If you store leeks in this kind of environment, they will stay fresh for at least 2 to 3 months, if not longer.
Store fresh leeks in the refrigerator. Seal them unwashed in a plastic bag, and they will keep for about a week.