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Vegetable gardening | how to grow leeks

by dig the dirt editor

Many a savory winter soup begins with a shivering dash to the garden to pick a wrist-thick leek from its sheltering bed. The ever-ready fortitude of the leek in winter is our reward for giving it garden space and occasional attention during its long, slow (up to 130-day) growing season.

Young leeks are best raised to maturity in trenches. Trench planting, and the subsequent slowly rising soil level it permits, encourages the development of a longer white stem—the tender part that is so good to eat. (If you plant leeks at the surface of the ground rather than in a trench, the tougher green leaves tend to flag off from the central stem closer to the ground, limiting the amount of edible stalk.) By the time winter arrives, these exceptionally cold-hardy plants are still growing, staunchly weathering snow and ice until we harvest them for dinner.

Fast-growing cultivars such as ‘Titan’ and ‘King Richard’ mature earlier, in mid- to late summer, but for winter harvest, select the much hardier traditional cultivars such as ‘Large American Flag’, ‘Unique’, ‘Blue Solaise’, ‘Nebraska’, and ‘Alaska’.

The old Scottish gardener who ritually buried the laird’s wool trousers under the leek row was, perhaps unwittingly, providing two of the conditions leeks like best: a deep root run and a ready supply of organic matter. For a superb stand, give the leeks deeply dug, well-drained, near-neutral or slightly acid soil rich in humus.


Wait until the seedlings are at least six inches (15 cm) high, then harden them off and plant in a trench about six inches (15 cm) deep and six inches (15 cm) wide. Just tuck the seedlings into the bottom, water well, and leave the trench open for the first few weeks until the plants get established. A wide-bottomed trench, dug with a shovel, is better than a V-shaped furrow; you don’t want the soil to sift back into the hole while the plants are still small, and you will need the working space the trench bottom will give you to cover the plants gradually as they grow.




The object here is to keep the soil level at, or just below, the point where the leek’s green leaves diverge from the stem, in order to help the plant build a longer stretch of pale stem. When the leaves are six to eight inches (15 to 20 cm) high, start to rake or hoe fine soil into the trench—only about an inch (2.5cm) at a time—every three weeks. Keep them well watered throughout this process. To beef up the soil’s humus content, substitute one inch (2.5cm) of fine compost for one inch (2.5 cm) of fine soil on one or two of the regular trench fillings.

Because the young seedlings are thready and easily overwhelmed by weeds, starting leeks from seed indoors is best. Sow seed in flats in January or February, later thinning the seedlings to stand one inch (2.5 cm) apart in each flat. Alternatively, plant leek seed directly in the ground three or four weeks before your last frost date; I’ve had good results from starting them in a space-saving nursery bed until they were ready for transplanting. Southern gardeners can plant leek seed in late summer for winter and spring crops.




Before the soil freezes hard, pile on 10 to 12 inches (25 to 30 cm) of mulch to keep the ground workable for another few weeks, and, later, to protect the leeks from extremely cold weather. If the ground freezes hard early in your area, you can replace some of the mounded-up soil with mulch to permit easier access to the plants. Straw, leaves, and aged sawdust make good weed-free mulches.




Leeks are extremely hardy, but if you are concerned about deep freezing, dig some up before the ground hardens completely and store them in sand in a cold cellar. You might need to use a fork; dig from the side of the row to avoid cutting into them. Otherwise you can probably harvest the plants right into January if you’ve mulched the ground thoroughly before it froze.




By early fall the trench will be filled in completely, and the once slender plants will have turned into stout, muscled stalks, all the more tender because you have blanched them as they grew. Continue to pull up soil around the bases of the plants every few weeks, stopping just before the green leaf pleats begin to fan out, so that the soil won’t wash down between the leaflets of the stalk. Hilling encourages the formation of additional inches of pale, tender stalk.


Before cooking, rinse the leeks thoroughly to wash out soil trapped between the looser upper layers. And keep an eye on the calendar. Before long, perhaps one day after you’ve enjoyed a warming bowl of cock-a-leekie soup, it will be time to start another crop of leeks. You can either plant more from seed or replant the corms (small bulbs) that cluster around the base of overwintered mother plants in early spring.


vegetable gardening, leeks, raising leeks