When to plant tomatoes 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). Tomato needs 60–85 days to mature, which fits comfortably within Illinois's growing season.
When to plant tomatoes in Illinois: the short answer
For a spring planting, plant out Apr 20 – May 7, with seeds started indoors Feb 23 – Mar 9. Wait until the soil is at least 50°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 tomatoes in Illinois, step by step
- Start seeds indoors (Feb 23 – Mar 9). Sow seeds ¼ inch deep in seed-starting mix under bright light. They take 5-10 days to sprout, fastest in soil around 80°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 7.5. Dig in compost before planting.
- Plant out (Apr 20 – May 7). Space plants about 24 inches apart in rows 36 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: tomato hornworm, aphids, whitefly, flea beetle. Diseases and disorders: early blight, late blight, septoria leaf spot, fusarium wilt, blossom-end rot (calcium disorder).
- Harvest (from about Jun 26 – Jul 21). Tomato takes 60-85 days to reach harvest. Days to maturity counted from transplant. Bury 2/3 of the stem at transplanting for extra roots. Determinate types suit containers and one big harvest; indeterminate types need staking and produce until frost.
Figures come from our crop data; dates use Illinois’s average frost dates. More in the full tomato growing guide.
Tomato 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 tomato dates shift with them.
When to plant tomatoes in nearby states
Questions gardeners in Illinois ask
When is the best time to plant tomatoes in Illinois?
Plant tomato transplants outdoors in Illinois between April 20 and May 7. That timing is set by Illinois's average last spring frost of April 20.
When should I start tomato seeds indoors in Illinois?
Start seeds indoors between February 23 and March 9, about 7 weeks before the last frost, so the seedlings are ready to plant out from April 20.
What is the latest I can plant tomatoes in Illinois?
About August 15. Tomatoes need at least 60 days to mature after transplanting, and frost around October 14 ends the season, so later plantings risk being cut short.
When will tomatoes planted in Illinois be ready to harvest?
Planted on time, tomatoes are usually ready from about June 26 to July 21, 60-85 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.