Colorado · zones 5a–7a
When to plant tomatoes in Colorado.
Sow or transplant between May 16 to Jul 16 in a typical year, keyed to Colorado's median last frost around May 9. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Tomatoes dates for a typical Colorado season.
1 · Start indoors
Apr 4 to Jun 4
About 6 weeks before set-out. Warm spot, real light.
2 · Set out
May 16 to Jul 16
Keyed to the ~May 9 last frost. Sow 0.25" deep, 24" apart.
Harvest
~73 days later
~12 lb per plant over ~8 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.