Leeks (Allium ampeloprasum)
This large, upright Allium variety does not form bulbs and matures into long, thick, blanched shanks with flat leaves that are 1 to 1 1/2 inches wide. Known for its hardiness and ease of care, it offers long, beautiful stems from autumn through spring, a time when other crops are scarce. With a mild onion flavor, both the green leaves and white shaft are edible. The plants grow to a height of two to three feet and have a width of approximately two inches.
Temperature
Plant leeks in full sun or partial shade. Transplant them once early spring weather stabilizes and daytime temperatures reach at least 45°F.
Soil
Leeks are heavy feeders and require fertile soil (pH of 6.2-6.8) for best results.
Planting
Sow in flats in Feb.–March, 1/4" apart, 1/4" deep. Transplant to 1 1/2" plug flats when large enough to handle, or start in plug flats, thinning to one plant per cell.
Transplanting: When approx. 8" tall and pencil-thick, transplant outdoors 6" apart in rows 24" apart using dibbled holes 6" deep. Only 1–2" of leaves need extend above the soil. Do not firm the soil—allow irrigation or rain to fill the holes.
Direct Seeding: Sow early spring, 6 seeds/ft., 1/4–1/2" deep, rows 24" apart. Thin to 6".
Blanching: To extend the edible white stem, hill soil around the plants two or three times or use cardboard tubes to exclude light before harvest.
Spacing
4–6" in-row and 18–36" between rows.
Harvest
When leeks reach desired size, lift with a fork, clean, and store near freezing in moist sand, soil, or peat. Trim roots and damaged leaves. Most leeks mature when stems exceed 1" thick. High-quality leeks have firm, white shafts 3" or longer, with no bulb. The dark blue-green tops remain upright at maturity. Leeks are frost-tolerant and some can withstand down to 20°F. Mulch to extend harvest into late fall or winter in milder regions.
For more information, please see links below:
Note: This information is summarized. Additional details and expanded guidelines can be found in our production sheets available in the Holmes Seed Grower's Guidebook.
Downloadable Copy: