Planting Guides

When to Plant Tomatoes in Chicago: Complete Guide + Best Varieties for Zone 6a

Chicago, Illinois
USDA Zone 6a
Last Frost: May 10
Last updated: October 30, 2025
Learn when to plant tomatoes in Chicago with specific dates for Zone 6a. Compare 6 varieties, get a complete timeline, and discover which tomatoes grow best in Illinois.
PPatricia "Pat" O'Brien
October 30, 2025
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Chicago tomato seedlings ready for Zone 6a spring planting with city skyline background

Image © PlantReference.org 2026
Quick Answer
Start tomato seeds indoors March 15-22 in Chicago. Transplant outdoors May 15-20 after last frost for optimal growth.
TL;DR
Start tomato seeds indoors March 15-22 for Chicago's Zone 6a climate. Transplant outdoors May 15-20 after last frost (May 9). Best varieties include Solanum lycopersicum 'Early Girl' and Solanum lycopersicum 'Stupice' for Chicago's 158-day growing season. Harvest begins mid-July through October 14.
Frequently Asked Questions

When should I start tomato seeds indoors in Chicago?

Start tomato seeds indoors March 15-22 for Chicago's Zone 6a climate. This timing gives seedlings 7-8 weeks to develop before transplanting after the May 9 last frost date. Starting earlier often results in leggy, overgrown seedlings that struggle after transplanting.

What's the best planting date for tomatoes in Chicago?

May 15-20 is the optimal transplanting window for Chicago tomatoes. While the last frost averages May 9, soil temperatures need to reach 55°F (13°C) for proper root establishment. Lake Michigan keeps soil cool longer than air temperatures suggest.

Which tomato varieties grow best in Chicago's Zone 6a?

Solanum lycopersicum 'Early Girl' and Solanum lycopersicum 'Stupice' are the most reliable choices for Chicago. These varieties tolerate cool weather and lake effect conditions better than heat-loving varieties. Solanum lycopersicum 'Cherokee Purple' also performs well in Chicago's humid summers.

How does Lake Michigan affect tomato growing in Chicago?

Lake Michigan creates cooler spring temperatures, higher humidity, and constant winds that affect tomato growing. The lake keeps soil temperatures low well past the last frost date, delays spring planting, and increases disease pressure from humidity. However, it also moderates extreme heat in summer.

Can I grow tomatoes in containers in Chicago?

Yes, container growing works excellent in Chicago's Zone 6a climate. Use 20-gallon containers minimum for indeterminate varieties and place them in locations protected from lake winds. Containers allow you to move plants during unexpected late spring cold snaps and extend the harvest season.

When do tomatoes ripen in Chicago?

Early varieties like Solanum lycopersicum 'Early Girl' ripen by mid-July, while late varieties like Solanum lycopersicum 'Brandywine' ripen in late August through September. Chicago's 158-day growing season provides ample time for most varieties to reach full maturity before the October 14 first frost.

What diseases affect tomatoes in Chicago?

Early blight is the most common problem in Chicago's humid summers, appearing as brown spots with yellow halos on leaves. Late blight can occur during cool, wet August weather. Septoria leaf spot also thrives in Chicago's humidity. Good air circulation and preventive copper sprays help manage these diseases.
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Written By
P

Patricia "Pat" O'Brien

Pat has been gardening in Milwaukee for over thirty years, through every kind of Wisconsin weather. She worked as a school librarian and started gardening seriously when her kids were small—she wanted them to know where food came from. Now retired, she's a certified Master Gardener and runs the plant sale at her local garden club every spring. She specializes in cold-hardy perennials, native wildflower meadows, and the art of getting a vegetable garden producing in Wisconsin's short but intense growing season. Pat is practical and patient—she's seen enough Wisconsin winters to know that gardening here is a long game, and she writes with the steady confidence of someone who's been doing this a long time.

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