Illinois · zones 5b–6b
When to plant zucchini in Illinois.
Sow between Apr 27 to Aug 10 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
Zucchini dates for a typical Illinois season.
Direct sow
Apr 27 to Aug 10
Keyed to the ~Apr 20 last frost. Sow 1" deep, 24" apart.
Harvest
~50 days later
~8 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 zucchini here.
A middle-length season, about 181 frost-free days, means squash, summer 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: Lay a board out overnight and collect them at dawn; scrape bronze egg clusters off leaf undersides.
Sudden wilt with sawdust-like frass at the stem base.
Organic fix: Cover young plants; slit the stem to remove the grub, or inject Bt.
Yellow striped or spotted beetles chewing leaves and blossoms.
Organic fix: Row cover until the first female flowers open, then hand-pick.
White powder coating the leaves late in the season.
Organic fix: Space for airflow, water the soil rather than the leaves, use resistant varieties.
Your season math: Illinois gives zucchini about 181 frost-free days, and it needs roughly 50 days to a first harvest. That fits about 5 re-sown rounds across the season, so you can keep it coming instead of picking once.
Planting zucchini in Illinois: questions
When should I plant zucchini in Illinois?+
In a typical Illinois year, sow zucchini between Apr 27 to Aug 10, 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 zucchini 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.