When to plant sunflower in Illinois
Illinois spans USDA zones 5a–7a, so the right time to plant sunflower shifts by weeks across the state. The window to sow seed directly outdoors runs from about April 4 in Granite City to May 1 in McHenry — below are local dates for 226 cities, each computed from its own frost dates.
| City | Zone | Last frost | First frost | Direct sow |
|---|---|---|---|---|
| Chicago | 6a | April 10 | November 5 | April 10 – May 1 |
| Aurora | 5b | April 19 | October 23 | April 19 – May 10 |
| Naperville | 5b | April 28 | October 16 | April 28 – May 19 |
| Joliet | 5b | April 19 | October 25 | April 19 – May 10 |
| Rockford | 5b | April 24 | October 17 | April 24 – May 15 |
| Elgin | 5b | April 26 | October 18 | April 26 – May 17 |
| Springfield | 6a | April 15 | October 22 | April 15 – May 6 |
| Peoria | 6a | April 16 | October 23 | April 16 – May 7 |
Sunflower in Illinois: FAQ
When can I plant sunflower in Illinois?
Across Illinois, the time to direct-sow sunflower spans roughly April 4 in Granite City to May 1 in McHenry, each following that city's local frost dates.
Does the sunflower planting date vary across Illinois?
Yes. Illinois publishes 226 cities with their own frost dates, so the right sunflower 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 sunflower take to grow in Illinois?
Sunflower takes about 70–100 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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