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.
In Colorado: watch for
The pests that find lettuce here.
The short season here, about 143 frost-free days, keeps lettuce, leaf in front of aphids only briefly. One early row cover usually carries a planting through the worst of it.
Clusters tucked into the heart of the head.
Organic fix: Rinse well; insecticidal soap on young plants.
Ragged holes and slime trails, worse after rain.
Organic fix: Iron-phosphate bait; a diatomaceous-earth ring; hand-pick at night.
Seedlings clipped off at the soil line overnight.
Organic fix: Collars around the stems; Bt or diatomaceous earth.
Pale yellow patches boxed in by the leaf veins, with white fuzz underneath.
Organic fix: Give plants room, let them dry between waterings, clear old leaves, and pick resistant varieties.
Your season math: Colorado gives lettuce about 143 frost-free days, and it needs roughly 45 days to a first harvest. That fits about 10 re-sown rounds across the season, so you can keep it coming instead of picking once.
Planting lettuce in Colorado: questions
When should I plant lettuce in Colorado?+
In a typical Colorado year, sow lettuce between Apr 1 to May 16, keyed to the state's median last frost around May 9. There's also a fall window: Jul 16 to Sep 14. Your exact dates shift with your ZIP code and microclimate.
What USDA zone is Colorado?+
Colorado spans zones 5a–7a, mostly zone 6. But frost dates, not zones, set planting time. The free planner uses your ZIP code's actual frost dates.
How many lettuce plants do I need?+
Depends who you're feeding. The crop page has exact counts per household size, or the free planner does the math for your family in about 60 seconds.