When to plant eggplants in Illinois
Illinois’s average last spring frost is April 20, and the first fall frost typically arrives around October 14 — about 177 frost-free days (USDA zones 5a, 5b, 6a, 6b, 7a). Eggplant needs 65–85 days to mature, which fits comfortably within Illinois's growing season.
When to plant eggplants in Illinois: the short answer
For a spring planting, plant out May 4 – May 21, with seeds started indoors Feb 9 – Feb 23. Wait until the soil is at least 70°F and frost is over.
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow eggplants in Illinois, step by step
- Start seeds indoors (Feb 9 – Feb 23). Sow seeds ¼ inch deep in seed-starting mix under bright light. They take 7-14 days to sprout, fastest in soil around 85°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. They need at least six to eight hours of direct sun a day and loose soil at least 18 inches deep, with a pH between 5.5 and 6.5. Dig in compost before planting.
- Plant out (May 4 – May 21). Space plants about 20 inches apart in rows 30 inches apart. It is killed by frost, so nothing goes outside until the danger has passed.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: flea beetle, Colorado potato beetle, aphids, spider mite. Diseases and disorders: verticillium wilt, phomopsis blight, bacterial wilt.
- Harvest (from about Jul 15 – Aug 4). Eggplant takes 65-85 days to reach harvest. The most heat-demanding common vegetable - do not rush it into cold soil. Flea beetles hammer young plants; a row cover until flowering pays off.
Figures come from our crop data; dates use Illinois’s average frost dates. More in the full eggplant growing guide.
Eggplant planting dates by USDA zone in Illinois
Illinois spans USDA zones 5a, 5b, 6a, 6b, 7a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the eggplant dates shift with them.
When to plant eggplants in nearby states
Questions gardeners in Illinois ask
When is the best time to plant eggplants in Illinois?
Plant eggplant transplants outdoors in Illinois between May 4 and May 21. That timing is set by Illinois's average last spring frost of April 20.
When should I start eggplant seeds indoors in Illinois?
Start seeds indoors between February 9 and February 23, about 9 weeks before the last frost, so the seedlings are ready to plant out from May 4.
What is the latest I can plant eggplants in Illinois?
About August 10. Eggplants need at least 65 days to mature after transplanting, and frost around October 14 ends the season, so later plantings risk being cut short.
When will eggplants planted in Illinois be ready to harvest?
Planted on time, eggplants are usually ready from about July 15 to August 4, 65-85 days after transplanting.
When is the last frost in Illinois?
On average around April 20, with the first fall frost around October 14 - about 177 frost-free days. Your town may differ by two weeks or more.