Botanical Name: Allium ampeloprasum
Days to Maturity: 75 days
Native: Eastern Mediterranean region
Hardiness: Biennial grown as an annual
Plant Dimensions: 18"–30" tall. Under optimal growing conditions, the white part of 'King Richard' can be 12" long, making the entire plant up to 30" long.
Variety Information: Leek plants resemble a long, fat green onion. The white lower portion has a mild onion flavor while the green tops are stronger tasting. Cold hardy to 20°F.
When to Sow Outside: 2 to 4 weeks before your average last frost date for late summer harvest, late spring for fall harvest, and in Mild Climates, late summer for the following spring harvest. Soil temperature should be at least 40°F, ideally 60°–85°F.
When to Start Inside: RECOMMENDED. 8 to 10 weeks before your average last frost date.
Days to Emerge: 7–14 days
Seed Depth: ¼
Seed Spacing: A group of 3 seeds every 6"
Row Spacing: 12"
Thinning: When 1" tall, thin to 1 every 6"
Harvesting: Harvest leeks when tops are 15"–18" tall, and shanks are at least 1" in diameter. Use a garden fork to gently lift and loosen soil under the leeks, and then pull them up by hand. Leeks tolerate temperatures as low as 20°F, and can therefore be harvested even after a few freezes, which enhances flavor.