Colorado · zones 5a–7a
When to plant lettuce in Colorado.
Sow between Apr 1 to May 16 in a typical year, keyed to Colorado's median last frost around May 9. A second, fall sowing fits Jul 16 to Sep 14. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Lettuce dates for a typical Colorado season.
Direct sow
Apr 1 to May 16
Keyed to the ~May 9 last frost. Sow 0.25" deep, 6" apart.
Fall round
Jul 16 to Sep 14
Counted back from the ~Sep 29 first frost.
Harvest
~45 days later
~0.4 lb per plant over ~1 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.