Heirloom. A member of the onion family, leeks are often called the gourmet’s onion because of their mild flavor. This version, called American Flag, is one of the favorite leeks for home gardens. The mild but flavorful long, leafy leeks are prized for casseroles, stir-fry, soups, and omelets. And, of course, they are a source of flavor and color in the classic leek and potato soup. Plants grow nice, 10-inch-long, white stalks about 1 to 1 ½ inches in diameter. American Flag is a frost-tolerant, cold-hardy leek, making it good for fall planting in zones 7 and warmer, easily growing where temperatures don’t drop below 10 degrees in winter, but they take longer to grow to full size. This also goes by the name Broad London leek.

  • Stalk size 10 inches
  • Matures 80 days
  • Plant spacing 6 inches apart
  • Plant size 15 to 18 inches tall

Some Bonnie Plants varieties may not be available in your local area, due to different variables in certain regions. Also, if any variety is a limited, regional variety it will be noted on the pertinent variety page.

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At a glance
Nutrition Information

Light requirements: Full sun.

Planting: Space 6 inches apart.

Soil requirements: All onions need well-drained, nutrient-rich soil. Work at least 3 inches of compost or other organic matter into soil prior to planting. Soil pH should be 6.0 to 6.8.

Water requirements: Keep soil consistently moist until bulbs enlarge. Onion roots are shallow; apply a light layer of mulch to slow water evaporation from the soil. Once the tops of the bulbs push through the surface, remove mulch to allow them to bask in the sun.

Frost-fighting plan: Onions tolerate even hard frosts (temperatures below 28º F). Still, protect newly planted seedlings from late spring frosts by covering plants with straw or a frost blanket.

Common issues: Onion thrips, aphids, and onion root maggots can cause problems.

Harvesting: Pull onions at any stage for fresh eating. Harvest young onions to eat as scallions. For full-sized bulbs, don’t pull onions until bulbs are big and tops start to yellow and fall over.

To harvest, pull onions and shake off soil. Before snipping roots or trimming tops, cure them in a warm, airy place. During curing, roots shrivel and necks dry and tighten. After 7 to 10 days of curing, clip onion tops and roots; rub dry dirt from bulbs, taking care not to remove papery outer skins.

Storage: Store cured, dried, full-size bulb onions in a cool place. Very sweet, juicy onions store best in the refrigerator. Use mild onions within a few weeks of harvest; pungent onions can store for 10 to 12 months.

For more information, visit the Onions page in our How to Grow section.

Nutrition Facts

1/2 cup chopped mature onions:
  • Calories: 30
  • Carbohydrates: 7g
  • Dietary fiber: 1.5g
  • Sugars: 3.5g
  • Protein: 1g
  • Vitamin C: 10% DV
  • Vitamin B6: 5%
  • Folate: 4%
  • Manganese: 5%
  • Potassium: 3.5%

Nutritional Information

The health benefits of onions are so numerous that it is impossible to list them all. Much of this benefit comes from powerful sulfur compounds, the same ones that account for the onion’s eye-watering odor. These compounds, along with chromium, a trace mineral in good supply in onions, and vitamin B6 have been found for help regulate blood sugar, lower total cholesterol and triglyceride levels, and lower blood pressure. Onions have also been found to boost intestinal and bone health and ward off several types of cancer. Researchers say that the more pungent the onion, the greater the load of beneficial phytonutrients.