When to plant onions
The rule
Days to maturity: 100–120 days [src]
Method: Start seeds indoors, then transplant. Frost tolerance: frost-hardy (derived from the planting timing above).
Onions is frost-hardy; it's grown as a spring/summer crop.
Onions planting dates by hardiness zone
| Zone | Start indoors | Transplant / sow | Sow for fall |
|---|---|---|---|
| Zone 2a | February 8 – February 22 | April 12 – April 26 | — |
| Zone 2b | February 16 – March 2 | April 20 – May 4 | — |
| Zone 3b | February 11 – February 25 | April 15 – April 29 | — |
| Zone 4a | February 5 – February 19 | April 9 – April 23 | — |
| Zone 4b | February 1 – February 15 | April 5 – April 19 | — |
| Zone 5a | February 3 – February 17 | April 7 – April 21 | — |
| Zone 5b | January 26 – February 9 | March 30 – April 13 | — |
| Zone 6a | January 22 – February 5 | March 26 – April 9 | — |
| Zone 6b | January 15 – January 29 | March 19 – April 2 | — |
| Zone 7a | January 7 – January 21 | March 11 – March 25 | — |
| Zone 7b | December 29 – January 12 | March 2 – March 16 | — |
| Zone 8a | December 18 – January 1 | February 19 – March 5 | — |
| Zone 8b | December 8 – December 22 | February 9 – February 23 | — |
| Zone 9a | November 24 – December 8 | January 26 – February 9 | — |
| Zone 9b | October 27 – November 10 | December 29 – January 12 | — |
| Zone 10a | October 9 – October 23 | December 11 – December 25 | — |
| Zone 10b | October 14 – October 28 | December 16 – December 30 | — |
What you'll need
Affiliate links — as an Amazon Associate we may earn from qualifying purchases, at no extra cost to you.
Seed-starting traysBurpee SuperSeed 36-cell trayReusable cells that pop seedlings out with the roots intact at transplant time.See it on Amazon- Seed-starting mixEspoma Organic Seed StarterA fine, sterile mix so small seeds can push through and seedlings don't rot.See it on Amazon
- Grow lightBarrina T5 LED grow lights, 4-packA windowsill is too dim in late winter; a light 2–3 in. above keeps seedlings short and sturdy.See it on Amazon
Ordering seeds or soil for this window? Amazon Prime includes fast delivery on eligible items, and eligible new members may be offered a free trial, so supplies ordered now can arrive while the window is still open. Delivery speed varies by item and address. See if you can try Prime free →
Affiliate link — we may earn a commission on qualifying sign-ups, at no extra cost to you. Current terms are on Amazon's page.
Calendar computed 2026-09-27. Sources: University of New Hampshire Cooperative Extension — “Growing Vegetables: When to Plant Your Vegetable Garden”; University of Georgia Extension — Vegetable Planting Chart (Circular C963) (days to maturity); NOAA NCEI 1991–2020 Climate Normals (frost); USDA 2023 Plant Hardiness Zone Map.