Root Vegetable

When to Plant Leeks

Mild, sweet onion relative that grows slowly but rewards patience with elegant flavor. Hardy through winter in many zones.

Sun

Full sun (6+ hours)

Water

1 inch per week

Days to Harvest

100-150

Difficulty

intermediate

Spacing

Frost Tolerance

high

The Short Answer

Leeks are best when soil temperature reaches at least 45°F. Enter your zip code on our homepage tool for exact dates.

How to Grow Leeks

Leeks are the gentle giants of the onion family — mild, sweet, and elegant in a way that onions and garlic never quite achieve. The edible white shaft is produced by blanching: gradually hilling soil around the stems as they grow to exclude light. The deeper you plant and the more you hill, the longer the white portion. Leeks are remarkably cold-hardy — in zones 6 and warmer, they can be harvested all winter long by simply pulling them from unfrozen soil. King Richard is fast for summer harvest; Blue Solaise is the cold-hardiest for winter garden use.

Starting Seeds Indoors

Begin leeks seeds indoors 10 weeks before your average last frost date. Seeds need soil temperatures of at least 45°F to germinate, which typically takes 10-14 days. Provide 12 hours of light per day using a south-facing window or grow lights.

Transplanting

Move seedlings outside 0 weeks after your last frost date, once soil temperatures reach 45°F. Harden off seedlings for 7 days before transplanting by gradually exposing them to outdoor conditions.

Growing Tips

Hill soil around stems as they grow to blanch the white shaft. Leeks are extremely cold-hardy — harvest through winter in zones 6+. Milder and sweeter than onions.

Companion Planting

Good companions:

Carrots Celery Onions

Keep away from:

Beans Peas

Leeks Planting Dates by State

Click your state for leeks planting dates specific to your location:

Note: Planting dates are based on average frost dates from NOAA Climate Normals (30-year averages). Actual conditions vary year to year. Always check your local forecast before planting frost-sensitive crops.

Last reviewed: March 29, 2026