Leeks look like an overgrown green onion with a long white body and thick overlapping leaves. Learn how to grow leeks, an easy-to-grow relative of the onion that has a milder taste and is grown for the thick white edible stalk.
Leeks can grow up to 3 feet tall. Leeks are a frost-tolerant vegetable that grows during the winter in mild winter areas and has a long growing season (120-150 days). Learn how to leeks with these 8 tips.
8 Tips for How to Grow Leeks
1. Plant leeks at the right time
Leeks grow best in temperatures between 55°F – 75°F. Transplant leeks outside as soon as the soil can be worked and daytime temperatures are at least 45°F.
2. Choose the best location to plant leeks
- Leeks grow best with at least 8 hours of direct sunlight.
- Choose a location with rich, loose, well-draining soil.
- Amend the planting area with a balanced organic fertilizer or compost before planting.
- Rotate where you plant other members of the onion family to help prevent pests and diseases such as root maggots.
How to plant leeks from seed:
- Start leek seeds indoors in seed starting trays 8-12 weeks before your last frost.
- When leek seedlings are about 2 inches tall, transplant them into individual containers.
- Fertilize young seedlings every 2 weeks with fish emulsion.
- Leeks are ready to transplant outside when they are the diameter of a pencil and between 6-12 inches tall.
- Trim the roots of transplants to about 1 inch long to make transplanting easier.
How to plant leeks from transplant:
4. “Hill” leeks as they grow
When growing leeks, the goal is to have a larger white (edible) part. You accomplish this by doing two things: planting transplants deeply and “hilling” the leeks as they grow.
Hill leeks by mounding soil up around the stems to produce a larger white stem. Mulch deeply to blanch stems as well.
5. Water leeks correctly
Leeks have a shallow root system and do best with regular watering.
- After planting, water leeks well.
- Water deeply after each application of fertilizer.
- Between fertilizing, water leeks once the top inch or so of dirt is dry.
- Yellow-tinged leaves are a sign of overwatering; cut back on water.
6. Feed leeks regularly during the growing season
Leeks are heavy feeders and benefit from regular additional fertilizer. Feed your leeks right after planting with an organic fertilizer high in phosphorus (the middle number on a fertilizer ratio).
Feed leeks again 3 weeks after planting with a high-nitrogen organic fertilizer (blood meal, manure, etc.). Continue to feed leeks about every 3 weeks during the growing season to encourage large leaves. Water well after each fertilizer application.
7. Harvest leeks as needed
When growing leeks from transplant, harvest as desired anytime 30 days after planting. Dig out or pull when large enough for use (usually when the stalk is between 1-2 inches).
Leeks prefer cool weather and in cool climates can be left in the garden to overwinter. If freezing temperatures are expected, mulch heavily.
Harvest leeks before temperatures get hot in warm climates like the low desert of Arizona. Use a garden fork to loosen soil before pulling. Trim leaves if desired.
If the center stalk of the leek becomes thick and tall, and then develops a flower stalk, the leek is bolting. During the growing season, leeks will occasionally bolt as a reaction to stress (cold, heat, lack of water, etc.). Bolted leeks must be eaten right away; they will not store well. If leeks bolt or flower during the season, harvest and use them as soon as possible.
8. Store and prepare leeks correctly
Grit and soil often become trapped in leek layers. Clean leeks thoroughly by slicing them in half lengthwise, separating layers and rinsing to remove all traces of dirt.
Leeks need cold temperatures to store well (near 32°F) and prefer high humidity to keep them from drying out. Store in plastic bags to preserve moisture. Leeks will keep for about 1 week in the fridge. You can also store leeks by freezing. For best flavor, do not thaw before eating. Enjoy this versatile vegetable in soups, stir-fried, raw, braised, or in quiche.