When to plant onion in Michigan
Michigan spans USDA zones 4b–6b, so the right time to plant onion shifts by weeks across the state. The window to transplant seedlings outdoors runs from about March 22 in Port Huron to April 21 in Cadillac — below are local dates for 101 cities, each computed from its own frost dates.
| City | Zone | Last frost | First frost | Transplant out |
|---|---|---|---|---|
| Detroit | 6b | April 27 | October 25 | March 30 – April 13 |
| Grand Rapids | 6a | May 6 | October 10 | April 8 – April 22 |
| Warren | 6b | April 21 | October 31 | March 24 – April 7 |
| Sterling Heights | 6b | April 30 | October 24 | April 2 – April 16 |
| Ann Arbor | 6a | May 5 | October 10 | April 7 – April 21 |
| Lansing | 6a | May 1 | October 13 | April 3 – April 17 |
| Dearborn | 6b | May 1 | October 15 | April 3 – April 17 |
| Livonia | 6b | May 1 | October 17 | April 3 – April 17 |
Onion in Michigan: FAQ
When can I plant onion in Michigan?
Across Michigan, the time to transplant onion spans roughly March 22 in Port Huron to April 21 in Cadillac, each following that city's local frost dates.
Does the onion planting date vary across Michigan?
Yes. Michigan publishes 101 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 Michigan?
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.
Never miss a window in your area
An email when it’s time to start seeds, transplant, and sow — timed to your frost dates. Double opt-in, one-click unsubscribe, no spam.