Climate Conditions for Growing Leeks
Leeks are very frost resistant, so they can overwinter in hardiness zone 7 or warmer climates. If you’re planting in a warm weather area, you can sow leeks in the fall for a spring harvest. If you’re living in a cooler climate, plant your leeks in early spring to harvest your leeks from summer through fall. Leeks thrive in full sun or partial shade with temperatures below 75°F (24°C).
Plant short-season leeks in the spring and you’ll have leeks through early fall. If you plant hardy, long-season leeks, you can plant them in the spring for northern climates or in the late summer for southern climates.
Soil Conditions for Leeks
Leeks grow well in well-drained, slightly acidic soil with a pH of 6.0 to 6.8. Adding organic matter, such as compost, manure or leaf clippings to the soil gives the leek stems the nutrition they need for healthy growth.
When to Start Leek Seeds
Start your leek seeds indoors from 2 to 3 months before the last frost for northern climates. If you’re planting in warmer climates, you can start your seeds indoors about 3 to 4 weeks before the last spring frost. In southern climates, you can also plant the leek seeds directly in the ground at the end of the summer. Your harvest will be ready for picking from winter to early spring.
The following lists the temperatures and timeline for germinating leeks:
- Starts germinating as low as 45°F (7°C)
- Best germination temperature is 77°F (22°C)
- Tolerates temperatures as high as 95°F (35°C)
- Seeds emerge within one week
When to Transplant Leek Seedlings
Move the leek seedlings outside when the temperature reaches 40°F (4.4°C). Before planting the leeks in your garden, harden them off for about one week, so they can adjust to outside life. You do this by putting the leeks outside during the day, and placing them in a sheltered area at night. Once your leeks are hardened off, they’re ready for your garden.