VegetableLeek
Large American Flag Leek
Large American Flag Leek is a cold-hardy cultivar of Allium ampeloprasum bred to thrive in northern climates, producing substantial white stems that swell as the plants mature beneath their flat green foliage. Ready to harvest in 130 to 139 days, this open-pollinated variety grows 18 to 24 inches tall and reaches full size with just 6 inches of spacing between plants, making it remarkably efficient for home gardens. The mild, slightly sweet flavor sets it apart from most onions, offering versatility in the kitchen without the sharp bite gardeners might expect from its Amaryllidaceae relatives.
Photo © True Leaf Market
Growing Conditions
USDA Zone
4-8
Sunlight
Full Sun
Water
Moderate
Soil
Well-drained, Fertile Loam
Growth Stats
24 in
Height
TypeUpright
Spacing
6
Plant Profile
Sunlight
Full Sun
Water
Moderate
Zones
4-8
Size
24in H x ?in W
Growth
—
Care
Moderate
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Highlights
Large American Flag Leeks develop impressively thick white stems that grow in girth as they mature, creating the substantial harvest this variety is named for. The cold tolerance that bred this cultivar into existence means it thrives in zones 4 through 8, even enduring frosts that would damage less hardy leeks. That mild, sweet onion-like character makes them far less pungent than standard onions, while the upright growth habit and modest spacing needs deliver surprising yields from compact garden footprints.
Common Uses
Slice these leeks into soups and stews where their mild sweetness provides depth without overwhelming other flavors, or use them in traditional English meat pies and French cuisine. The white stems can be braised whole as a side dish, while both white and light green portions work beautifully in salads. Their gentle onion-like character makes them far more approachable than raw onions for cooks who want aromatic flavor without harshness.
Growing Timeline
No timeline data available yet for this variety.
Care Instructions
Start Indoors
Start seeds indoors 10 to 12 weeks before your last spring frost, maintaining soil temperatures between 50 and 70 degrees Fahrenheit for reliable germination. Keep seedlings under bright light once sprouted to prevent legginess, and transplant into individual cells or pots when they develop their first true leaves.
Transplant Outdoors
Transplant seedlings outdoors after hardening off for 7 to 10 days, spacing them 6 inches apart in rows 16 inches apart once soil temperatures consistently reach 50 degrees Fahrenheit or warmer. Bury the white stems slightly deeper than they grew indoors to encourage additional blanching and stem development.
Direct Sow
Direct sow seeds outdoors in spring once soil temperatures reach 50 degrees Fahrenheit, planting seeds thinly at the spacing depths listed and thinning seedlings to final spacing once they develop several true leaves.
Harvesting
Harvest Large American Flag Leeks once they reach 18 to 24 inches in height and have developed thick white stems, typically 130 to 139 days after planting. Dig carefully around the base of each leek and pull upward to harvest the entire plant with its roots intact, or use a garden fork to loosen the soil before pulling. The variety's frost-hardy nature means you can leave mature leeks in the ground through light frosts, harvesting them as needed rather than all at once.
Growing Calendar
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Companion Planting
Ecology & Traits
Edible
Scientific Classification
Allium ampeloprasum
Family
Amaryllidaceae
Genus
Allium
Growth Habit
Upright
Native Status
L48 (I)
History & Origin
“The American Flag Leek represents decades of deliberate selection for cold hardiness and stem size, developed specifically for home gardeners in northern climates who needed a leek variety resilient enough to overwinter or tolerate early frosts. Unlike European heirloom leeks adapted to milder regions, this cultivar was bred to endure cold weather while maintaining the mild, sweet flavor that makes leeks distinctive within the onion family. The variety emerged from open-pollinated breeding programs focused on practical American gardening conditions, becoming a staple for households seeking reliable, flavorful leeks without requiring protected growing environments.”