Illinois · zones 5b–6b
When to plant cucumbers in Illinois.
Sow between Apr 27 to Jul 27 in a typical year, keyed to Illinois's median last frost around Apr 20. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Cucumbers dates for a typical Illinois season.
Direct sow
Apr 27 to Jul 27
Keyed to the ~Apr 20 last frost. Sow 1" deep, 12" apart.
Harvest
~60 days later
~5 lb per plant over ~5 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 cucumbers here.
A middle-length season, about 181 frost-free days, means cucumber, slicing overlaps squash bugs for a stretch each summer. Check plants every week or two and treat early.
Gray shield bugs; leaves wilt and get crispy patches.
Organic fix: Crush the copper egg rows under leaves; diatomaceous earth at the base.
Yellow striped or spotted beetles that spread bacterial wilt.
Organic fix: Row cover until the first female flowers open; neem for heavy runs.
Angular yellow patches bounded by the leaf veins, after wet foliage.
Organic fix: Water in the morning, space for airflow, pull badly infected vines.
White powder coating the leaves late in the season.
Organic fix: Space for airflow, water at the base, spray neem.
Your season math: Illinois gives cucumbers about 181 frost-free days, and it needs roughly 60 days to a first harvest. That fits about 6 re-sown rounds across the season, so you can keep it coming instead of picking once.
Planting cucumbers in Illinois: questions
When should I plant cucumbers in Illinois?+
In a typical Illinois year, sow cucumbers between Apr 27 to Jul 27, keyed to the state's median last frost around Apr 20. 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 cucumbers 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.