By Barbara Fahs, Garden Guides Contributor
Leeks (Allium ampeloprasum) add a sweet onion taste to any recipe calling for common onion. They are easy to grow and can endure cold weather, enabling a harvest during the colder months for a fresh winter vegetable that adds so much flavor to your favorite dishes. Similar in appearance to scallions, only larger, leeks provide a good serving of manganese, vitamin C, iron and vitamin B6, while it adds few calories and helps to reduce cholesterol and blood pressure.
Leeks like good soil, such as crumbly loam, but it will survive in many soil types. The most important thing is to plant them in an area that is at least 12 inches deep. Being a good winter crop, leeks thrive in soils that are about 60 degrees. Their flavor is best after a frost.
Cooked or raw, leeks add a bonus taste to soups, salads, stir-fry and any recipe calling for onions. They are at their tastiest from fall through early spring.
Choosing a Variety
Summer leeks mature at the end of summer, and they are smaller and sweeter than the overwintering variety. But if you want a spring harvest the year after you plant them, winter leeks are larger and more strongly flavored.
Leek seeds are available through nurseries and catalogs and are easy to start. They are compact, so you can plant them thickly. Just make sure to give them plenty of space for their roots to roam deep. Plant leek seeds directly in the garden in early spring, or in flats indoors in late winter. If you get a jump on the season this way, transplant them when they are 2 inches tall, after your final frost.
After your seeds sprout or your transplants are in the ground, keep the soil moist as long as your leeks are growing. Fertilizing once a month with fish emulsion helps them to grow to be big and delicious. Leeks can suffer from downy mildew, so watch for a powdery substance on the leaves and spray with organic sulfur if you see it. They are also prone to onion maggots and thrips, while they can help reduce the number of aphids, Japanese beetles and carrot flies that inhabit your garden and bother other plants.
Harvesting and Storing Leeks
Pull your leeks when they are firm and straight, about 2 feet tall, with dark green leaves and white necks, with a diameter of about 1 inch. Wash thoroughly in chilled water, and then store them in a plastic bag in the refrigerator, where they will keep fresh for 1 to 2 weeks. After you cook leeks, they won't stay fresh for long, so enjoy them right away. You can freeze leeks: blanch them for 2 to 3 minutes, and then store in freezer bags. They will remain good for about 3 months.