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Leek (American Flag) is the standard leek variety for North American home gardens — a long-season allium that develops thick, ivory-white shanks with an arching flag of blue-green tops, producing one of the mildest, most versatile allium flavors in the kitchen. American Flag leeks have a sweet, buttery onion character without the sharp bite of onions or the pungency of garlic, making them invaluable for dishes where subtlety is key: French vichyssoise, leek and potato soup, Welsh cawl, risotto, braised leeks with cream, and pasta sauces where the allium should support rather than dominate. The plants grow to 15–18 inches with shanks averaging 6–8 inches in usable white length when properly blanched by earthing up. American Flag is remarkably cold-hardy, standing in the garden through hard frosts and producing a continuous harvest from October through early winter.
Start American Flag leeks indoors 10–12 weeks before last frost, sowing seeds thinly in trays and transplanting into individual cells once seedlings are large enough to handle. Transplant outdoors in spring as soon as the soil is workable — leeks tolerate hard frosts and actually develop better flavor in cool soil. The critical technique for producing the long white shanks that make leeks worth growing is blanching: as the plant grows, gradually mound or "earth up" soil, compost, or shredded leaves around the stems, covering the green portion and extending the pale, blanched shank downward. This can also be achieved by planting into a 6-inch-deep trench and filling in gradually as plants grow. Space plants 6 inches apart in rows 12 inches wide. Water consistently through summer and fall — consistent moisture produces thicker, more tender shanks than drought-stressed plants. Feed monthly with a balanced fertilizer through midsummer. American Flag leeks are fully cold-hardy and improve in flavor after fall frosts. Harvest by digging rather than pulling to avoid breaking the shank; a border fork inserted 4–6 inches away and levered gently lifts the roots without damage. Leeks left in the ground through winter will bolt in spring — harvest any remaining plants before flower stalks emerge.
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