When to plant onion in Missouri
Missouri spans USDA zones 5b–7b, so the right time to plant onion shifts by weeks across the state. The window to transplant seedlings outdoors runs from about February 26 in Sikeston to March 24 in Kirksville — below are local dates for 87 cities, each computed from its own frost dates.
| City | Zone | Last frost | First frost | Transplant out |
|---|---|---|---|---|
| Kansas City | 6b | April 4 | November 2 | March 7 – March 21 |
| St. Louis | 7a | April 1 | November 4 | March 4 – March 18 |
| Springfield | 7a | April 4 | October 27 | March 7 – March 21 |
| Columbia | 6b | April 5 | October 31 | March 8 – March 22 |
| Independence | 6b | April 10 | October 27 | March 13 – March 27 |
| Lee's Summit | 6b | April 7 | October 29 | March 10 – March 24 |
| O'Fallon | 6b | April 10 | October 26 | March 13 – March 27 |
| St. Charles | 6b | April 8 | October 29 | March 11 – March 25 |
Onion in Missouri: FAQ
When can I plant onion in Missouri?
Across Missouri, the time to transplant onion spans roughly February 26 in Sikeston to March 24 in Kirksville, each following that city's local frost dates.
Does the onion planting date vary across Missouri?
Yes. Missouri publishes 87 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 Missouri?
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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