When to plant fennel (bulb) in Colorado
Colorado spans USDA zones 5b–7a, so the right time to plant fennel (bulb) shifts by weeks across the state. The window to transplant seedlings outdoors runs from about March 31 in Grand Junction to June 7 in Edwards — below are local dates for 70 cities, each computed from its own frost dates.
| City | Zone | Last frost | First frost | Transplant out |
|---|---|---|---|---|
| Denver | 6a | May 4 | October 8 | April 20 – May 4 |
| Colorado Springs | 6a | May 3 | October 8 | April 19 – May 3 |
| Aurora | 6a | May 7 | October 8 | April 23 – May 7 |
| Fort Collins | 5b | May 2 | October 7 | April 18 – May 2 |
| Lakewood | 6a | May 3 | October 7 | April 19 – May 3 |
| Thornton | 6a | May 2 | October 11 | April 18 – May 2 |
| Arvada | 6a | May 5 | October 5 | April 21 – May 5 |
| Westminster | 6a | May 2 | October 11 | April 18 – May 2 |
Fennel (Bulb) in Colorado: FAQ
When can I plant fennel (bulb) in Colorado?
Across Colorado, the time to transplant fennel (bulb) spans roughly March 31 in Grand Junction to June 7 in Edwards, each following that city's local frost dates.
Does the fennel (bulb) planting date vary across Colorado?
Yes. Colorado publishes 70 cities with their own frost dates, so the right fennel (bulb) 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 fennel (bulb) take to grow in Colorado?
Fennel (Bulb) takes about 65–90 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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