UC Master Gardeners, Santa Clara County, CA
University of California
UC Master Gardeners, Santa Clara County, CA


Garden Help > Vegetables

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Photo: University of California
Photo: University of California
How to grow: Growing Onions & Leeks, Center for Agroecology and Sustainable Food Systems (CASFS), UC Santa Cruz

Pest management: Leeks are subject to similar pests and diseases as Onion and Garlic

The Basics

Leeks are members of the Allium family that do not form bulbs like their onion and garlic relatives. Instead, they develop a 6–10" edible stem that can be up to 3" diameter.

When to plant

  • Transplant Aug–Sept
  • To grow your own transplants from seed, start them 10–12 weeks earlier
  • Leek seedlings are relatively easy to separate so transplants can be grown densely in pots

Harvest window: Harvest at desired size: ½–1" diameter for baby leeks, 1–2" for mid-size, or 2–3" for full size. Large ones generally require 100-120 days to mature.

Care overview

  • Plant baby leeks 1-2" apart,  mid-size leeks 4–8" apart, and full size 8-10" apart
  • For long blanched shanks, plant seedlings in a hole up to the first leaf.
  • For additional length, plant seedlings at the bottom of a V-shaped trench. Fill in the trench and hill soil up around the stems as they grow.

Recommended Varieties for Santa Clara County*

Carentan, OP Long, thick leek grows strong and vigorously, with a delicate and delicious flavor. Up to 2 inches across. An old European heirloom variety. 18–24" tall. Plant 4–6" apart 

* Many other varieties may also do well here in Santa Clara County. This list is based on UC Master Gardener trials, taste tests, and feedback from local growers.

Webmaster Email: webmaster-mgsantaclara@ucanr.edu