When to plant onion in Washington
Washington spans USDA zones 6b–9a, so the right time to plant onion shifts by weeks across the state. The window to transplant seedlings outdoors runs from about February 1 in Port Townsend to May 2 in Cheney — below are local dates for 132 cities, each computed from its own frost dates.
| City | Zone | Last frost | First frost | Transplant out |
|---|---|---|---|---|
| Seattle | 9a | March 8 | November 23 | February 8 – February 22 |
| Spokane | 7a | April 26 | October 15 | March 29 – April 12 |
| Tacoma | 8b | March 8 | November 14 | February 8 – February 22 |
| Vancouver | 8b | March 29 | November 9 | March 1 – March 15 |
| Bellevue | 9a | March 8 | November 23 | February 8 – February 22 |
| Kent | 8b | March 20 | November 10 | February 20 – March 6 |
| Everett | 8b | March 24 | November 2 | February 24 – March 10 |
| Spokane Valley | 7a | April 26 | October 15 | March 29 – April 12 |
Onion in Washington: FAQ
When can I plant onion in Washington?
Across Washington, the time to transplant onion spans roughly February 1 in Port Townsend to May 2 in Cheney, each following that city's local frost dates.
Does the onion planting date vary across Washington?
Yes. Washington publishes 132 cities with their own frost dates, so the right onion planting window shifts by weeks between the warmest and coldest parts of the state — use your city's page for the exact dates.
How long does onion take to grow in Washington?
Onion takes about 90–110 days to reach harvest once planted — check that this fits inside your city's frost-free season on its place page.
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