You'll find cold weather is no impediment when you grow leeks, a subtle yet flavorful cousin to onions and garlic. And you can harvest them right through the winter.
A growing number of American gardeners and cooks are discovering that they love to grow leeks and cook leeks (Allium porrum). Though the leek was prized by Egyptian pharaohs, Roman emperors and European kings, it seems its sweet, subtle flavor has been upstaged in recent years by onions and garlic, its more assertive cousins. Big in size and deliciously mild in flavor, leeks are wonderfully versatile in the kitchen. You can use them cooked or uncooked; in soups, stews, casseroles and salads; or prepared simply on their own for an easy and satisfying winter dish. What’s more, leeks are one of the most durable vegetables you can grow. By selecting the right varieties, you can enjoy this tasty, nutritious crop year-round — including the dead of winter — making it a must for both home and market gardens.
You’ll find several leek varieties in seed catalogs, usually grouped by harvest time: summer, fall and winter. Most leeks can be harvested over a long period of time; in fact, the most cold-hardy varieties will maintain their good quality for months in the ground. “That’s the beauty of cold-hardy crops,” says John Navazio, director of education and research for the Organic Seed Alliance in Port Townsend, Wash. “Even though growth slows from around mid-October until early March, you can still harvest them at any time.” (Leek plants are biologically programmed to survive the winter months so they can flower and produce seed the second year.) Depending on snow cover and how far north you live, you’ll need to add enough leaves or straw to keep the ground from freezing so you can continue to harvest your leeks during the cold months. (Plastic bags of leaves work great, and are easy to remove when it’s time to dig.)
The most cold-hardy leeks — and best candidates for winter and spring harvest — usually are the ones with the longest “days to maturity.” Other clues to cold hardiness include leaf color and length of “stem” (the tender, white portion). As a rule of thumb, leeks with blue leaves and short, thick stems survive winter better than those with green leaves and tall, slender stems.
Organic market grower Sean Albiston of Blue Roof Organics in Stillwater, Minn., extends his harvest by growing ‘Varna,’ a tall and slender leek, for late summer to fall harvests and ‘American Flag’ and ‘Blue Solaise,’ two venerable heirlooms, for winter to spring harvests. All three varieties perform well in his cold Minnesota garden.
‘King Richard’ and ‘Giant Musselburgh’ also make an excellent combination for extended harvest, Navazio says. “‘King Richard’ is a good summer and fall leek — it’s nice and uniform but not very cold hardy. ‘Giant Musselburgh,’ which is shorter, is quite cold hardy. Even down to 15 degrees, most of the crop survives, so you can harvest it in January and February.”
‘Giant Musselburgh’ and ‘Blue Solaise’ also have proven winter hardy in the southeastern Pennsylvania garden of MOTHER EARTH NEWS contributing editor William Woys Weaver. A leek connoisseur, Weaver notes in his book Heirloom Vegetable Gardening that ‘Musselburgh’ “stands on its own … the tough reliability of this one takes it past a long list of leeks with much fancier names.”
Plan now to order your leek seeds as early as possible. (You probably won’t find leek transplants at garden centers.) Most gardeners start leeks indoors in January or February, then transplant to the garden in early spring. A second crop of cold-hardy winter leeks can be started in March, then transplanted by early summer.
For best results, sow the seeds in individual cells, plugs or soil blocks, filled with a loose, well-aerated seed-starting mix. Albiston makes his mix using equal parts compost and peat mixed with a little bit of greensand, rock phosphate, dolomitic lime and sea kelp to supply micronutrients.
Like other seedlings started indoors, leeks want all the light you can give them. A bright windowsill, greenhouse or cold frame can provide the right light, but a pair of fluorescent bulbs also will do, if you keep them no further than an inch or two above the seedlings.
About 8 to 10 weeks after you sow the seeds, the little leeks should be just big enough to transplant to their garden home. Before you settle them in the garden, though, “harden them off” in a shady outdoor spot for a week or two, until the plants have acclimated to the brighter, windier conditions.
To avoid damage by diseases and insect pests that linger in soil, choose a planting site where onions, garlic or other alliums have not grown for several years. A raised bed amended with plenty of organic matter will help provide the loose, rich soil that leeks love.
Weaver has built up the soil in his leek beds over many years, using “lots of sand and aged horse manure.” He says, “It’s important to have leek beds that hold the moisture during hot weather, but which also drain well in the winter. You don’t want standing water, which will form ice in winter. Ice can kill the leeks at the crown.”
Plant the seedlings about 6 inches apart in the prepared bed. For winter harvest in extremely cold climates, you can plant the seedlings directly in a hoop house.
In order to harvest leeks with tender, white shanks (the portion below the leaves), it is worth going to the trouble to blanch them in the garden. Blanching is the practice of deliberately blocking light from the green parts so they will become white and tender. Traditionally, leek growers do this by gradually hilling up soil around the growing stems. Jeff Cantara, who grows 1,500 leeks annually at his New Roots Farm in Newmarket, N.H., suggests a better way: Plant the seedlings in a furrow, then gradually fill in the soil as the leeks grow.
“This works better than hilling up because it keeps the roots moist,” Cantara says. “I don’t need to irrigate at all.” Before transplanting, he digs a 5- to 6-inch-deep furrow, then dusts the bottom lightly with an organic fertilizer. “We rely primarily on compost and cover crops, but a little supplemental fertilizer goes a long way with leeks,” he explains. “By putting the fertilizer in the bottom of the furrow, it goes to the leeks’ root zone — not to the weeds.” The leek seedlings are anchored in place inside the furrow with a small amount of soil, and more soil is added gradually over the following weeks.
After the furrow is completely filled with soil, mulch the bed with a layer of straw or shredded leaves to help retain moisture, impede weed growth and blanch more of the stems. Weed control is essential because leeks don’t like to compete for water and nutrients. An occasional feeding of fish emulsion fertilizer also will keep your leeks growing strong.
Pests and diseases are not a big problem with leeks, especially if you rotate beds. Occasionally, onion maggots will kill some seedlings or yellow the leaves of larger plants. Just pull out the affected plants as soon as you see them. Onion thrips, a minute winged insect, also can stunt growth and damage leaves: dust diatomaceous earth (available at garden centers) on the leeks to help control this pest.
Leeks are easygoing when it comes time to harvest. You can pretty much dig them as needed, starting in August for the summer and fall varieties. Even small, immature leeks make tasty additions to salads, soups and stir-fries. Dig only the amount you plan to use because leeks store best right in the ground. Leek roots can be extensive, so use a hand fork to unearth them gently.
For winter harvest, cover your leeks with dry leaves or a plastic tunnel just before the first hard freeze. This will help extend the harvest even for varieties that aren’t winter-hardy, such as ‘King Richard.’ “We harvest most of our crop in fall but always leave at least some of the plants in the ground for winter harvest,” Cantara says. “Even if the plants don’t look good above ground, there’s still 6 to 7 inches of stalks below ground that are great for winter soups.”
The most cold-hardy varieties, including ‘Giant Musselburgh,’ ‘American Flag’ and ‘Blue Solaise,’ will hang on through winter in most regions, then resume growing in March when temperatures warm. Keep a close eye on the plants in the spring; you want to harvest before they flower and produce seed — usually by the end of April — when they will turn woody. From January into April, however, these long-lived leeks are at their best, displaying the genetic hardiness that gardeners and cooks have appreciated for millennia. In fact, if you try this sturdy vegetable, you’ll discover it is not only the last crop standing, but also the first to mature in each new season.
‘King Richard,’ ‘Lincoln,’ ‘Rikor,’ ‘Kalima,’ ‘Titan’
Fall/Early Winter Leeks
‘Varna,’ ‘Imperial,’ ‘Tadorna,’ ‘Falltime’
‘American Flag,’ ‘Blue Solaise,’ ‘Giant Musselburgh,’ ‘Siegfried,’ ‘Winter Giant’
Vicki Mattern is a contributing editor for MOTHER EARTH NEWS magazine, book editor and freelance magazine writer. She has edited or co-authored seven books on gardening, and lives and works from her home in northwestern Montana. You can find Vicki on Google+.