Colorado · zones 5a–7a
When to plant broccoli in Colorado.
Sow or transplant between Mar 18 to Apr 15 in a typical year, keyed to Colorado's median last frost around May 9. A second, fall sowing fits Jun 15 to Jul 25. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Broccoli dates for a typical Colorado season.
1 · Start indoors
Feb 4 to Mar 4
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
Mar 18 to Apr 15
Keyed to the ~May 9 last frost. Sow 0.5" deep, 18" apart.
Fall round
Jun 15 to Jul 25
Counted back from the ~Sep 29 first frost.
Harvest
~60 days later
~1.2 lb per plant over ~3 weeks.
Colorado spans more than one climate: Zone 6 is the most common zone, but the state runs 5a to 7a. That's why the planner works from your ZIP code's frost dates, not your zone — mountain and coastal gardens in the same state can be three weeks apart.