Fort Collins, CO · zone 6a · ~156 frost-free days
When to plant in Fort Collins: frost dates and zone 6a.
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 | — |
| Cucumber, slicing | — | May 10 to Jul 20 | — |
| 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.
Fort Collins planting questions
What planting zone is Fort Collins, CO?+
Fort Collins is in USDA hardiness zone 6a. Growing zone, gardening zone, and planting zone all mean the same thing: the USDA number, 6a here. It tells you what survives winter, not when to plant. Frost dates set your planting time, and the free planner uses your exact ZIP code's frost dates, which can differ by weeks across one metro.
When is the last frost date in Fort Collins?+
The typical last spring frost in Fort Collins, CO is around May 3. That is an average from local history, not a guarantee, so tender crops like tomatoes and peppers are safer with a week of buffer after it.
When is the first frost date in Fort Collins?+
The typical first fall frost in Fort Collins, CO arrives around Oct 6, closing a growing season of roughly 156 frost-free days. Count backward from it to find the last date a fall crop can still finish.
What can I plant now in Fort Collins?+
It depends on the date. Cool-season crops like lettuce, kale, and spinach go out weeks before the last frost; warm-season crops like tomatoes and peppers wait until after May 3. The table above shows each crop's window; the free planner turns your ZIP into an exact, dated calendar.