Grow and Save Leek Seeds

How to Grow Leeks

Leeks have been used as a culinary crop for at least 4,000 years. Enjoy this historic allium in your garden and try your hand at biennial seed saving.

Time of Planting

Sow leek seeds indoors 8-10 weeks before the last frost date. Seedlings can be transplanted outside as soon as the risk of hard frost has passed.

Spacing Requirements

Plant leek seeds ¼ inch deep into flats. When transplanting leeks into your garden, space them 6 inches apart.

Time to Germination

5-7 days

Special Considerations

Leeks like soil rich in organic matter. They’re also a heavy feeder—meaning they prefer a high-nitrogen fertilizer.

Common Pests and Diseases

Leeks can suffer from downy mildew, white rot, and leaf blight. Take care to rotate plant families in your garden to prevent diseases.

When and How to Harvest for Food Consumption

Harvest leeks when they reach a diameter of between ½ to 1-½ inches. Take care to thoroughly wash your leek plants before cooking with them; dirt can accumulate between their tall leaves.

Eating

Leek can be used in many recipes that call for onions. The flavor and texture of leek holds up to a lot of cooking, so use leeks in soups, stews, and other simmered dishes.

Storing

Whole leeks will store for weeks in a refrigerator and months in a root cellar.

How to Save Leek Seeds

It may take additional time and effort to cultivate leeks for seeds rather than for eating, but because this biennial crop is fairly cold hardy, it can overwinter in the garden in many regions.

Life Cycle

Biennial

Recommended Isolation Distance

Separate varieties by 800 to ½ mile in their second year of growth.

Recommended Population Sizes

To ensure viable seeds, save seeds from at least 5 plants. When maintaining a variety over many generations, save seeds from 20-50 plants. If you’re saving seeds for genetic preservation of a rare variety, save seeds from 80 plants.

Vernalization

To produce seed from leeks, select several perfect leeks and store them through winter. Ideally, store leeks in a cool, dry space away from sunlight. Replant leeks in early spring using the same spacing used in their first year of growth. Staking leeks to prevent lodging during flowering is recommended.

Assessing Seed Maturity

Seed maturity occurs in the second growing season, when capsules split open to expose mature black seeds.

Harvesting

To harvest, cut the scape about 6 to 8 inches below the seed head. The harvested umbels should be placed in an open container or bag, or on a screen, to continue drying in a well-ventilated space for at least seven days. A longer drying period can make threshing easier, especially if many fruits were still green at harvest.

Cleaning and Processing

After the plants bloom and seed heads begin to dry, gather the heads in a paper bag and shake the seeds free. Allow the seeds to air-dry for a few days before storing the seeds in a cool, dry place.

Storage and Viability

Leek seeds will remain viable in cool, dry storage for a couple of years.

Read more about storing seeds.

Growing Biennials for Seed (Video)

Former Seed Savers Exchange field manager Bryan Stuart plants one-year old ‘Schnittporree’ leeks that spent the winter months in the root cellar. Leeks are a biennial crop that produce seed at the end of the second year.

Because of our harsh winters in northern Iowa, we dig up biennial crops at the end of their first year, put them in a root cellar for the winter, then plant them out again the following spring.