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.

DDorothy "Dot" Williams

October 30, 2025

Chicago tomato seedlings ready for Zone 6a spring planting with city skyline background — — Image © PlantReference.org 2025

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.

Product Recommendations

Burpee Self-Watering Tomato Growing Kit with 20-Gallon Container

https://www.burpee.com/self-watering-tomato-kit-prod003456.html

Complete container growing system includes 20-gallon self-watering planter, premium potting mix, and organic fertilizer. Self-watering reservoir maintains consistent soil moisture crucial for preventing blossom end rot in Chicago's variable weather. Built-in water gauge eliminates guesswork for new gardeners. Sturdy construction handles Chicago's lake winds and urban conditions. Includes detailed growing guide specific to container tomato culture. Perfect for balconies, patios, and small urban spaces common in Chicago neighborhoods.

Price: $24.99-$29.99

Johnny's Seeds Zone 6a Tomato Variety Pack - Chicago Climate Tested

https://www.johnnyseeds.com/vegetables/tomatoes/collections/zone-6a-tomato-collection.html

Professionally curated seed collection featuring six varieties specifically tested for Zone 6a conditions. Includes Early Girl, Stupice, Cherokee Purple, San Marzano, Sungold, and Brandywine varieties mentioned in this guide. Each packet contains 25-30 seeds with detailed growing instructions for Chicago-area climate. Seeds are tested for cold germination and disease resistance relevant to Great Lakes region. Backed by Johnny's 50+ years of vegetable breeding expertise. Organic seed options available for sustainable Chicago urban gardens.

Price: $18.95-$22.95

REOTEMP Heavy Duty Soil Thermometer with 6-inch Stainless Steel Probe

https://www.amazon.com/REOTEMP-Heavy-Soil-Thermometer-Stainless/dp/B000BD7VG0

Professional-grade soil thermometer with 6-inch probe reaches proper depth for accurate soil temperature readings. Large 2-inch dial displays temperatures from 0-220°F, perfect for determining when Chicago soil reaches the critical 55°F transplanting threshold. Stainless steel probe resists corrosion from Chicago's clay soil conditions. Heavy-duty construction survives repeated use season after season. Hermetically sealed dial protects against humidity and condensation. Essential tool for timing tomato transplanting in Zone 6a climate where soil temperatures lag behind air temperatures.

Price: $12.99-$16.99

Bonide Copper Fungicide Concentrate for Organic Disease Control

https://www.amazon.com/Bonide-775-Copper-Fungicide-16oz/dp/B000BWA0L8

OMRI-listed organic copper fungicide concentrate effectively prevents and controls early blight, late blight, and septoria leaf spot common in Chicago's humid climate. Active ingredient copper octanoate provides excellent disease protection without harsh synthetic chemicals. One 16-oz bottle makes up to 16 gallons of spray solution, enough to protect large tomato plantings throughout the growing season. Works preventively when applied before disease pressure builds in June. Safe for use on food crops with no pre-harvest interval required. Compatible with organic certification standards for urban sustainability programs.

Price: $14.99-$18.99

Gardener's Supply Company Heavy-Duty Tomato Cages - Wind Resistant Design

https://www.gardeners.com/buy/heavy-duty-tomato-cages/8599509.html

Extra-heavy 11-gauge galvanized steel construction stands up to Chicago's constant lake winds and supports indeterminate varieties up to 8 feet tall. Unique square design with 5-inch grid openings allows easy harvesting while providing maximum support. Each cage measures 54 inches tall with 18-inch diameter, perfect for proper plant spacing in raised beds. Powder-coated finish resists rust and corrosion from Chicago's humid conditions. Easy assembly with no tools required. Collapses for winter storage in Chicago's limited urban spaces. Set of 6 cages handles typical home garden tomato plantings.

Price: $34.99-$42.99

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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Tagged with

#chicago tomatoes #zone 6a planting #illinois gardening #urban tomato growing #lake michigan gardening #midwest vegetables #tomato planting dates #chicago garden timing #illinois growing season #urban container gardening

Written By

Dorothy "Dot" Williams

Dot grew up on a small farm in rural Virginia and has maintained a vegetable garden for decades. After retiring from teaching elementary school, she became a Master Gardener volunteer and spends her time mentoring new gardeners at community garden plots in Richmond. She's especially knowledgeable about heirloom varieties, seed saving, and traditional growing methods passed down from her grandmother. Dot's no-nonsense advice comes from extensive trial and error—she's seen every tomato disease, pest problem, and weather disaster imaginable. Her biggest pet peeve is gardeners who overcomplicate simple tasks. "Plants want to grow," she often says. "Your job is to not get in their way."