Fort Collins, CO · zone 6a · ~156 frost-free days
When to plant a garden in Fort Collins.
In Fort Collins, the typical last spring frost lands around May 3 and the first fall frost around Oct 6, giving you about 156 frost-free days. Cool-season crops go out before the last frost; warm-season crops wait until after it.
The 2026 windows
Sow dates for Fort Collins, keyed to your frost.
| Crop | Start indoors | Spring sow / set out | Fall sow |
|---|---|---|---|
| Tomato, slicing | Mar 29 to May 29 | May 10 to Jul 10 | — |
| Lettuce, leaf | — | Mar 26 to May 10 | Jul 23 to Sep 21 |
| Carrot | — | Mar 26 to Apr 28 | Jul 11 to Aug 6 |
| Bush Bean | — | May 3 to Jun 23 | Jun 22 to Jul 25 |
| Cucumber, slicing | — | May 10 to Aug 9 | Jun 5 to Jul 6 |
| Pepper, bell | Apr 7 to May 29 | May 19 to Jul 10 | — |
| Kale | Feb 12 to Mar 12 | Mar 26 to Apr 23 | Jul 6 to Aug 21 |
| Spinach | — | Mar 12 to Apr 23 | Jul 23 to Sep 10 |
Fort Collins sits in Zone 6a, but two gardens in the same city can be a week or two apart. The planner works from your ZIP code's frost dates, not the zone, so the dates land right for your block, not the metro average.
Build your Fort Collins garden plan.
Tell the free planner what you want to eat and who you're feeding. It returns plant counts, spacing, and frost-safe sow dates for ZIP 80521 in about 60 seconds.