Start indoors or direct sow?

Start indoors and transplant for the best use of garden space and an earlier crop. Leeks tolerate transplanting very well, and young plants can be set deeply to create longer white shanks.

When to start Leeks seeds

Start seeds indoors about 8 to 10 weeks before the last spring frost. Transplant 2 to 4 weeks before the last frost or around that date, because leeks tolerate cool conditions after hardening off.

How to sow the seeds

Sow seeds 1/4 inch deep in sterile seed-starting mix in cell packs, plug trays, or a shallow container. Keep them in a warm location until they sprout, then grow them under bright lights.

Germination

Leek seeds usually germinate in 7 to 14 days. Soil around 65 to 75 F and evenly moist mix promote uniform germination.

Seedling care

Give seedlings strong light and keep the mix lightly, consistently moist. Thin clumps if needed, trim overly long leaf tips to about 3 to 4 inches to keep plants manageable, and provide airflow to discourage damping off.

Transplanting & hardening off

Harden seedlings off for 7 to 10 days before moving them outdoors. Plant pencil-thick seedlings in deep holes or trenches, set roots deep without filling the hole completely, then water so soil settles around the roots.

Tips

Fresh leek seed generally germinates better than old seed. Do not worry if transplants look thin, as they gain size after settling into the garden.

General seed-starting guidance for US home gardens; timing depends on your local frost dates and variety. Page updated Aug 4, 2026.