University of California
UC Master Gardener Program of Sonoma County
Leeks
Leeks are a member of the same family that includes onions, chives and garlic, but they do not form bulbs and have a milder flavor. Lower parts of stems, 3-10 inches, are white, tender, and 1-3 in. in diameter. Leeks are a welcome fall and winter crop but may be grown year round near the coast.
Direct Sow or Transplant
- Leeks are successful in mild summer microclimates when planted in spring or fall. In hot summer microclimates, plant only in late summer or fall.
- Amend soil, especially heavy clay, with ample compost to loosen soil, provide nutrients and retain moisture.
- Enrich poor soil with organic fertilizer such as fish emulsion.
- Sow seed indoors February-June to transplant April-June (6-8 weeks after seeding) in regions where summers are mild, or direct sow March-April.
- Sow seed indoors May-June for transplanting August-September in hot summer microclimates where they grow best as a fall crop.
- Opt to purchase transplants from nurseries. Leeks are sold either in bundles or 6-packs, usually in groups of several dozen.
- Tease apart seedlings and plant each one separately at least 2 in. apart for harvesting baby leeks, 4-8 in. apart to allow for mature growth, in rows 12 in. apart.
- Prepare a 4-5 in. deep trench in the planting row to sow seeds or set transplants up to the first leaf joint; gradually fill in soil around stems as they grow to blanch them.
Growth, Care, Harvest
- Plan on a long growing season, about 100 days to harvest with most varieties, but leeks may be left in the ground much longer, even several months.
- Mound up soil around stems when leeks are planted at ground level to encourage blanching.
- Continue filling in planting trench as leeks grow to produce long, edible stems.
- Mulch with an organic material to keep beds weed-free and evenly moist.
- Water regularly to avoid dry soil; provide irrigation in the absence of fall and winter rains.
- Leave plants in the ground over winter but harvest before the ground warms in spring.
- Leeks are generally ready to harvest when they are about 1” in diameter, but check the specific variety that you planted, as size at maturity can vary.
- Dig, rather than pull to harvest very long leeks to avoid breaking them.
- Leave leeks in the soil over winter, if you prefer, after they mature but harvest before consistent spring warmth or they will flower and go to seed. Leeks are biennials grown as annuals.
- Expect flowering and seed production if leeks are left in the ground for a 2nd Edible portions will be less tender; bulbils in flower clusters may be planted for a new crop.
Additional Information
- Sonoma County Master Gardener Vegetable Planting Summary.
- https://sonomamg.ucanr.edu/Food_Gardening_with_Less_Water/
- http://ipm.ucanr.edu/home-and-landscape/onions-and-garlic/index.html
February 2022