Leeks are a long season vegetable that's planted in spring in the North for a fall harvest, and late summer in the South for a winter harvest.
Leek leaves are edible, but are tough and chewy. They're best in stews or composted.
Considered in France as the "asparagus of the poor", this onion family vegetable isn't as popular in America as it is in England and Europe. That's too bad. Leeks are easy to grow, have a tasty, mild onion flavor that's great in soups, stir fries, stews, and roasted, and withstand cold weather making them a great fall and winter crop when little else is being harvested from the garden. Like many vegetables, the flavor of leeks sweetens once it's touched by cold weather. The plant is as beautiful as it tastes and, I think, much more attractive than onions in the garden. The mild-flavored white shafts (stems) open into attractive, thick, large, blue-green leaves. Leeks can be interplanted with flowers, such as mums and asters, and herbs, such as parsley, to provide a nice contrast in the fall garden.
Like all onion family crops, leeks are good for you, too. They are an excellent source of vitamin A, beta carotene, lutein, and folate. Plus, this hardy plant can withstand a frost and provide a green vegetable when few other greens are available. As late as December in Vermont, I have let leek plants freeze in the garden, thaw in the morning sun, and then harvested and sauteed them that evening.
Leeks take a long time to mature, so be patient. They taste best maturing in cool weather so depending on where you live, consider your options for planting times. Varieties vary in their maturity dates and cold hardiness. If growing leeks in fall to overwinter in a warm winter area (USDA zone 7 and warmer), select ones that are cold tolerant. If growing leeks in spring for a fall harvest in a cold winter areas, select fast maturing varieties. Also, look for attractive blue-green leaved varieties to add an ornamental touch.
Here are some varieties of leeks to try in your yard. Days to maturity from transplanting are listed after each variety. If direct seeding into the garden add 20 to 30 days.
'Bandit' (120 days) – This newer variety produces thick shafts on attractive blue-green leaves. It's very winter hardy.
'Giant Musselburgh' (105 days) – This Scottish heirloom has 2- to 3-inch thick shafts, is very cold tolerant, has a mild flavor, and smooth, tender stalks. It's very late to bolt in spring.
'King Richard' (75 days) – This fast maturing leek is good for cold winter areas. It produces tall, thick shafts, up to 1-foot long, with a tender flavor.
'Lancelot Hybrid' (75 days) – A fast maturing leek, 'Lancelot' has a thicker shafts than 'King Richard' and has attractive blue-green leaves.
'Tadorna' (100 days) – This disease resistant variety is fast growing, has blue green leaves, and moderate cold tolerance.
Harvest leeks as you need them since they can hold in the garden for weeks and withstand a frost.
Blanched white leek shafts are tender and mild tasting.
In cold winter areas, plant leek seeds indoors 8- to 10- weeks before your last frost for transplanting into the garden on or around the last frost date. Leek transplants are now becoming more readily available in garden centers for purchase in spring as well. In warm winter areas, sow seeds indoors or directly into the garden in late summer or plant transplants in fall when you would garlic or onions.
On all but sandy soils, create raised beds 8- to 10-inches tall, 3-feet wide, and as long as you like. Amend the soil with a 1- to 2-inch thick layer of compost before planting. Direct sow seeds 1-inch apart in rows 18 inches apart. Thin to 6 inches apart. Transplant seedlings when they are the diameter of a pencil, to 6 inches apart in trenches dug 8 inches wide and deep.
As the leek plants grow, slowly let the trench fill to cover the shafts. This will begin the blanching process. Blanched shafts are white, milder flavored, and have a more tender texture than green stems.
Keep leek beds evenly moist and weed free. Leeks don't compete well with weeds. Hill the plants twice during the growing season, mounding soil around the stems. This will force the leaves to form higher up the shaft, creating a longer blanched stem.
Leeks love fertilizer. Apply an organic fertilizer such as 5-5-5 monthly to keep them growing strong. Leeks have few pests and diseases.
Harvest spring planted leeks in fall after cool weather has sweetened their flavor. When the shafts are at least 1/2-inch in diameter and the white shaft is at least 3-inches long, pull the plants, remove the roots and top leaves. Although the leaves are edible, they are thick and chewy, so are best removed and composted. Cold tolerant varieties, such a 'Bandit', can be allowed to freeze in the garden and still be harvestable. To protect plants so they last longer into winter, mulch leeks with a 6- inch thick layer of hay or straw after a hard frost.
Harvest fall planted leeks through the winter and into early spring. During cold winters, consider mulching the plants as described above. Complete harvesting in spring before the leek plant sends up a flower stalk. The plants become tougher once the flower stalks form.
When using leeks in the kitchen, wash the layers carefully as they tend to accumulate soil from the garden. Leeks will last stored in plastic bags in the refrigerator for up to 1 week