When to plant sweet potato in Illinois
Illinois spans USDA zones 5a–7a, so the right time to plant sweet potato shifts by weeks across the state. The window to transplant seedlings outdoors runs from about April 25 in Granite City to May 22 in McHenry — below are local dates for 226 cities, each computed from its own frost dates.
| City | Zone | Last frost | First frost | Transplant out |
|---|---|---|---|---|
| Chicago | 6a | April 10 | November 5 | May 1 – May 15 |
| Aurora | 5b | April 19 | October 23 | May 10 – May 24 |
| Naperville | 5b | April 28 | October 16 | May 19 – June 2 |
| Joliet | 5b | April 19 | October 25 | May 10 – May 24 |
| Rockford | 5b | April 24 | October 17 | May 15 – May 29 |
| Elgin | 5b | April 26 | October 18 | May 17 – May 31 |
| Springfield | 6a | April 15 | October 22 | May 6 – May 20 |
| Peoria | 6a | April 16 | October 23 | May 7 – May 21 |
Sweet Potato in Illinois: FAQ
When can I plant sweet potato in Illinois?
Across Illinois, the time to transplant sweet potato spans roughly April 25 in Granite City to May 22 in McHenry, each following that city's local frost dates.
Does the sweet potato planting date vary across Illinois?
Yes. Illinois publishes 226 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 Illinois?
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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