Illinois · zones 5b–6b
When to plant garlic in Illinois.
Illinois's window for garlic runs on the fall side of the season. A second, fall sowing fits Oct 18 to Nov 2. Dates below are state medians; your ZIP code shifts them by days to weeks.
The 2026 windows
Garlic dates for a typical Illinois season.
Fall round
Oct 18 to Nov 2
Counted back from the ~Oct 18 first frost.
Harvest
~240 days later
~0.2 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 garlic here.
A middle-length season, about 181 frost-free days, means garlic overlaps onion thrips for a stretch each summer. Check plants every week or two and treat early.
Silvery streaks and curled leaf tips in hot spells.
Organic fix: Insecticidal soap or neem; hang sticky traps.
Seedlings wilt; white maggots in the bulb base.
Organic fix: Float a row cover over the row; rotate beds each year.
Pale patches with fuzzy gray growth in damp weather.
Organic fix: Space for airflow, water early in the day, spray neem.
White rot
Yellowing and dieback, then wilt; fluffy white mold at the bulb base and roots so rotted the plant lifts straight out.
Organic fix: No cure once it is in the soil. Plant clean stock, never follow onions with onions, and keep infested soil off tools and boots.
Your season math: Illinois gives garlic about 181 frost-free days, and it needs roughly 240 days to a first harvest. It's a one-planting crop, so time that single sowing well.
Planting garlic in Illinois: questions
When should I plant garlic in Illinois?+
Illinois's window for garlic is in fall: Oct 18 to Nov 2, keyed to the first fall frost around Oct 18.
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 garlic 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.