Colorado · zones 5a–7a
When to plant zucchini in Colorado.
Sow between May 16 to Aug 29 in a typical year, keyed to Colorado's median last frost around May 9. A second, fall sowing fits Jun 15 to Jul 4. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Zucchini dates for a typical Colorado season.
Direct sow
May 16 to Aug 29
Keyed to the ~May 9 last frost. Sow 1" deep, 24" apart.
Fall round
Jun 15 to Jul 4
Counted back from the ~Sep 29 first frost.
Harvest
~50 days later
~8 lb per plant over ~5 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.