History
American Flag Leek — also known as Large American Flag or Broad London — is one of the most celebrated heirloom leeks in the American garden tradition, with roots tracing back to 19th-century European kitchen gardens. Brought to the United States by immigrant gardeners who prized its reliability and exceptional flavor, it quickly became a staple of the American vegetable garden and a fixture in seed catalogs throughout the 1800s and early 1900s. Leeks themselves have been cultivated for over 3,000 years — beloved by the ancient Egyptians, Greeks, and Romans as a food of both sustenance and sophistication. American Flag remains the gold standard of heirloom leeks: thick, upright, and deeply flavorful, with the mild sweetness that makes leeks one of the most versatile vegetables in the kitchen. Open-pollinated and non-GMO.
Plant Profile
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Days to Maturity: 70–120 days from transplant
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Stalk Size: Thick, upright stalks 1–2 inches in diameter, 6–9 inches of white shank
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Leaves: Broad, flat, blue-green leaves with a classic flag-like appearance
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Plant Type: Open-pollinated, non-GMO heirloom biennial grown as an annual
Flavor Profile
American Flag Leeks have a mild, sweet, and subtly onion-like flavor that is far more delicate than a standard onion — without the sharpness or bite. The white shank is tender and silky when cooked, developing a rich, buttery sweetness that deepens with slow cooking. Raw, they offer a gentle allium flavor perfect for salads and garnishes. Cooked, they melt into soups, gratins, and braises with an elegance that few vegetables can match. Their flavor is complex enough to anchor a dish on its own, yet mild enough to complement nearly any ingredient.
Growth Type & Harvest Yields
American Flag is a vigorous, upright grower that produces impressively thick stalks from a modest garden footprint. Plants grow 18–24 inches tall with broad, flat leaves and a long, blanched white shank that develops as you hill soil around the base. Start seeds indoors for the longest growing season and transplant after the last frost. A planting of 20–30 leeks will provide an abundant harvest for fresh use, storage, and cooking throughout fall and into winter. Leeks are cold-hardy and improve in flavor after light frosts.
Disease Resistance
- Good resistance to leek rust in typical garden conditions
- Excellent cold hardiness — survives light frosts and improves in flavor after cold exposure
- Rarely troubled by pests — strong allium oils deter most insects
- Tip: Avoid overwatering and ensure good drainage to prevent rot at the base
Growing Tips & Planting Dimensions
- Spacing: 6 inches between plants in rows 12 inches apart
- Sow depth: ¼ inch deep indoors; transplant seedlings when pencil-thin
- Germination: 10–14 days at soil temps of 65–75°F
- Full sun — at least 6 hours of direct sunlight daily
- Prefers rich, well-drained soil with consistent moisture
- Hill soil around the base as plants grow to blanch and lengthen the white shank
- Transplant deeply — set seedlings 4–6 inches deep to maximize shank length
🌱 Good Things Come in Small Packages
Leek seeds are small — but don’t let their size fool you. These seeds carry everything needed to grow into tall, impressive stalks with long white shanks. They just ask for a little extra care at germination. Follow these steps and you’ll be well on your way.
How to Germinate Successfully:
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Start with the right foundation. Use a fine seed-starting mix or sift your mix before filling your tray — coarse particles can bury small seeds unevenly and work against good germination.
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Cover lightly — do not bury deep. Press seeds into the surface and cover with approximately ¼ inch of finely sifted mix. Leek seeds do not require light to germinate, but should not be pressed deep.
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Mist, don’t drench. Use a spray bottle to keep the surface evenly moist. Watering from above can wash small seeds away before they ever get started.
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Warmth is your friend. These seeds germinate best at 65–75°F — basically normal room temperature. A heat mat can help if your space runs cool.
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Trap the humidity. Cover your tray with a humidity dome or a loose piece of plastic wrap. This keeps moisture and warmth stable while you wait.
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Give them time. Germination typically takes 10–14 days. Keep conditions consistent, resist the urge to overwater, and trust the process — they will sprout.
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Thin with scissors, not fingers. Once seedlings appear, snip extras at the soil line rather than pulling. These roots are close together and pulling one can disturb its neighbors.
When to Plant
Start seeds indoors 10–12 weeks before your last frost date. Transplant outdoors after frost danger has passed when seedlings are pencil-thin (about 6–8 inches tall). Leeks can also be transplanted in late summer for a fall and winter harvest. Find your frost dates and hardiness zone at the USDA Plant Hardiness Zone Map.
Companion Plants & Mutual Benefits
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Carrots — leeks deter carrot fly; carrots deter leek moth — a classic pairing
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Celery — benefits from leeks’ pest-deterring allium oils
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Brassicas (Broccoli, Cauliflower, Brussels Sprouts) — leeks repel aphids and cabbage worms
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Marigolds — complement leeks’ pest-deterring properties throughout the bed
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Avoid planting near: beans and peas — alliums inhibit legume growth
How to Enjoy
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Soups & Stocks: The defining ingredient in potato leek soup — silky, sweet, and deeply satisfying
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Gratins & Braises: Slow-cook in butter or cream for an elegant side dish that pairs with roasted meats
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Quiches & Tarts: Sautéed leeks add a mild, sweet depth to egg dishes and savory pastries
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Roasted: Halve and roast with olive oil and thyme until caramelized and tender
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Raw: Thinly sliced young leeks add a gentle allium note to salads and grain bowls
Why Gardeners Love American Flag Leek
- One of the most reliable and productive heirloom leeks available — a true garden classic
- Mild, sweet flavor that is far more versatile than onions in the kitchen
- Thick, impressive stalks with a long white shank — beautiful and productive
- Excellent cold hardiness — extends the harvest deep into fall and early winter
- Open-pollinated and non-GMO — save your own seeds year after year
- A staple of American kitchen gardens since the 1800s
Harvest Tips
- Harvest when stalks reach 1 inch or more in diameter — typically 70–120 days from transplant
- Loosen soil with a fork before pulling to avoid breaking the shank
- Leeks can be left in the ground through light frosts — flavor improves with cold
- Trim roots and dark green tops before storing; refrigerate for up to 2 weeks
- For long-term storage, blanch and freeze sliced leeks for use in soups and braises all winter
Seed Saving
American Flag Leek is open-pollinated and a true biennial — it flowers and sets seed in its second year. To save seed, overwinter a few plants in the ground or in a cold frame, then allow them to bolt and flower in spring of year two. Tall flower stalks will rise and produce globe-shaped umbels. Allow the seed heads to fully dry on the plant before harvesting — cut the entire stalk and hang upside down over a paper bag to catch seeds as they fall. Store in a cool, dry, dark place in a labeled envelope. Leek seeds remain viable for 2–3 years under proper storage conditions.
Order Today
Add American Flag Leek Seeds to your garden this season and grow one of the most elegant and flavorful vegetables in the heirloom tradition. Choose your pack size and begin to grow.
