When to plant sweet potato in Maine
Maine spans USDA zones 5a–6a, so the right time to plant sweet potato shifts by weeks across the state. The window to transplant seedlings outdoors runs from about May 16 in Lewiston to June 6 in Sanford — below are local dates for 13 cities, each computed from its own frost dates.
| City | Zone | Last frost | First frost | Transplant out |
|---|---|---|---|---|
| Portland | 6a | April 26 | October 15 | May 17 – May 31 |
| Lewiston | 5b | April 25 | October 19 | May 16 – May 30 |
| Bangor | 5a | May 4 | October 4 | May 25 – June 8 |
| South Portland | 6a | April 26 | October 15 | May 17 – May 31 |
| Auburn | 5b | April 25 | October 19 | May 16 – May 30 |
| Biddeford | 6a | May 9 | October 3 | May 30 – June 13 |
| Sanford | 5b | May 16 | September 30 | June 6 – June 20 |
| Saco | 6a | April 26 | October 15 | May 17 – May 31 |
Sweet Potato in Maine: FAQ
When can I plant sweet potato in Maine?
Across Maine, the time to transplant sweet potato spans roughly May 16 in Lewiston to June 6 in Sanford, each following that city's local frost dates.
Does the sweet potato planting date vary across Maine?
Yes. Maine publishes 13 cities with their own frost dates, so the right sweet potato 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 sweet potato take to grow in Maine?
Sweet Potato takes about 90–120 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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