Growing Guide
 
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Leeks

Vegetable (Cool Season) - Onion Family

Allium ampeloprasum
Alliaceae Family

Milder flavored than most other onion-family crops, you can mulch long-season varieties in fall for winter and spring harvest.

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Site Characteristics
Sunlight:
  • full sun
  • part shade

Soil conditions:

  • requires well-drained soil
  • requires high fertility
Well-drained, rich soil, high in organic matter. Optimum pH is 6.2 to 6.8. Requires plentiful, even moisture for good yields.
Plant Traits

Lifecycle: annual

Biennial grown as an annual.

Ease-of-care: moderately difficult

Height: 2 to 3 feet

Spread: 0.5 to 1 feet

Foliage color:

  • medium green
  • dark green

Long-season varieties have a dark, bluish-green color.

Foliage texture: medium

Shape:

  • upright
  • fan-shaped
Special Considerations
Tolerates:
  • frost - More frost-tolerant than other cultivated onions.
Special characteristics:
  • not native to North America - Cultivated in Egypt more than 4,000 years ago.
Special uses:
  • edible landscaping
Growing Information
How to plant:

Propagate by seed

Germination temperature: 45 F to 95 F - Peak germination around 77 F.

Days to emergence: 5 to 7

Seed can be saved 3 years.

Maintenance and care:
Choose a weed-free, well-drained location. Raised beds are ideal. Leeks are good for intercropping with other garden plants, especially early-maturing spring greens. Do not plant where other onion family crops have been grown in the past 3 years.

You can direct-seed leeks, or start transplants indoors. Long-season varieties are best started indoors.

Start transplants about 8 to 10 weeks before last frost date. Sow seeds in flats about inch apart and inch deep. Transplant to cell-type containers when they are about 2 inches tall. If you skip this step and continue growing in open flats, simply tease apart and trim roots when transplanting into the garden.

Around the average last day of frost, set hardened-off transplants 4 to 8 inches deep, 4 to 6 inches apart, in rows 20 inches apart. Deep planting reduces need for hilling to blanch the base of the plants. Transplants should be about 6 to 12 inches tall - the bigger, the better. Only a few inches of leaf need to show above the soil.

Direct seed about 4 weeks before average last frost inch deep, 1 inch apart, in rows 20 inches apart. Thin to 4 to 6 inches apart.

Hill or mound soil around stems several times to blanch as leeks grow. (A single large hilling while plants are young can cause them to rot.) Or, place a portion of cardboard paper towel center around the lower part of the stem.

Leeks have shallow root systems and need consistent moisture and good weed control. Water weekly if weather is dry, and mulch to retain moisture and suppress weeds.

Pests:
Onion maggot - Use floating row covers to prevent infestations.

Thrips

Diseases:
Purple blotch (Alternaria porri)
Botrytis leaf blight
Varieties
Browse leek varieties at our Vegetable Varieties for Gardeners website.

Grow early or nonhardy varieties for summer harvest. They mature in as little as 50 days after transplanting and will withstand some frost.

Grow late or hardy varieties for fall and winter harvest. They take can take 100 or more days to mature, but can withstand heavy freezes. If well-mulched in fall, they can be harvested through winter and into spring in many places.

Elephant garlic (great-headed garlic) is a member of this species. See garlic for more information.

Some varieties recommended for New York include:

American Flag
Broad London
Electra
King Richard
Pancho