When to plant sunflower in Colorado
Colorado spans USDA zones 5b–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 14 in Grand Junction to June 21 in Edwards — below are local dates for 70 cities, each computed from its own frost dates.
| City | Zone | Last frost | First frost | Direct sow |
|---|---|---|---|---|
| Denver | 6a | May 4 | October 8 | May 4 – May 25 |
| Colorado Springs | 6a | May 3 | October 8 | May 3 – May 24 |
| Aurora | 6a | May 7 | October 8 | May 7 – May 28 |
| Fort Collins | 5b | May 2 | October 7 | May 2 – May 23 |
| Lakewood | 6a | May 3 | October 7 | May 3 – May 24 |
| Thornton | 6a | May 2 | October 11 | May 2 – May 23 |
| Arvada | 6a | May 5 | October 5 | May 5 – May 26 |
| Westminster | 6a | May 2 | October 11 | May 2 – May 23 |
Sunflower in Colorado: FAQ
When can I plant sunflower in Colorado?
Across Colorado, the time to direct-sow sunflower spans roughly April 14 in Grand Junction to June 21 in Edwards, each following that city's local frost dates.
Does the sunflower planting date vary across Colorado?
Yes. Colorado publishes 70 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 Colorado?
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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