Illinois · zones 5b–6b
When to plant lettuce in Illinois.
Sow between Mar 13 to Apr 27 in a typical year, keyed to Illinois's median last frost around Apr 20. A second, fall sowing fits Aug 4 to Oct 3. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Lettuce dates for a typical Illinois season.
Direct sow
Mar 13 to Apr 27
Keyed to the ~Apr 20 last frost. Sow 0.25" deep, 6" apart.
Fall round
Aug 4 to Oct 3
Counted back from the ~Oct 18 first frost.
Harvest
~45 days later
~0.4 lb per plant over ~1 weeks.
Illinois spans more than one climate: Zone 6 is the most common zone, but the state runs 5b to 6b. 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 Illinois: watch for
The pests that find lettuce here.
A middle-length season, about 181 frost-free days, means lettuce, leaf overlaps aphids for a stretch each summer. Check plants every week or two and treat early.
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: Illinois gives lettuce about 181 frost-free days, and it needs roughly 45 days to a first harvest. That fits about 14 re-sown rounds across the season, so you can keep it coming instead of picking once.
Planting lettuce in Illinois: questions
When should I plant lettuce in Illinois?+
In a typical Illinois year, sow lettuce between Mar 13 to Apr 27, keyed to the state's median last frost around Apr 20. There's also a fall window: Aug 4 to Oct 3. Your exact dates shift with your ZIP code and microclimate.
What USDA zone is Illinois?+
Illinois spans zones 5b–6b, 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.