Planting Guides
When to Plant Tomatoes in Milwaukee: Complete Guide + Best Varieties for Zone 5b
Milwaukee, Wisconsin
USDA Zone 5b
Last Frost: May 15
Last updated: December 5, 2025
Learn when to plant tomatoes in Milwaukee with specific dates for Zone 5b. Compare 6 varieties, get a complete timeline, and discover which tomatoes grow best in Wisconsin.
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Quick Answer
Start tomato seeds indoors March 31 for Milwaukee Zone 5b. Transplant outdoors May 21-28 after last frost risk passes.
TL;DR
Start tomato seeds indoors by March 31 in Milwaukee for Zone 5b success. Transplant outdoors May 21-28 after Milwaukee's average last frost of May 14. Solanum lycopersicum 'Early Girl' and Solanum lycopersicum 'Stupice' are essential for Wisconsin's 139-day growing season, while Solanum lycopersicum 'Sungold' provides reliable early harvests before September 30 frost.
Frequently Asked Questions
Can I direct sow tomatoes in Milwaukee?
Direct sowing isn't recommended in Milwaukee's Zone 5b climate. Our 139-day growing season is too short for most varieties to mature from direct-sown seeds. Even ultra-early varieties like Solanum lycopersicum 'Stupice' need the head start from indoor seed starting to produce substantial harvests before our September 30 average first frost. Start seeds indoors March 31 for best results in Milwaukee.
Do I need season extension in Zone 5b Milwaukee?
Season extension significantly improves success with heat-loving varieties in Milwaukee. Solanum lycopersicum 'Brandywine' and Solanum lycopersicum 'Cherokee Purple' benefit from Wall-o-Water protection at transplant and row covers if early fall frost threatens. However, early varieties like Solanum lycopersicum 'Early Girl' and {Solanum lycopersicum 'Sungold'} typically mature fully without protection in Milwaukee's climate.
Which tomato varieties handle Milwaukee humidity best?
Solanum lycopersicum 'Early Girl' and Solanum lycopersicum 'Sungold' handle Milwaukee's Lake Michigan humidity exceptionally well due to their F1 hybrid disease resistance packages. Both carry resistance to Verticillium and Fusarium wilts plus Tobacco Mosaic Virus. Solanum lycopersicum 'Cherokee Purple' shows better humidity tolerance than most heirlooms, while Solanum lycopersicum 'Brandywine' struggles with fungal diseases in Milwaukee's humid conditions.
When should I start hardening off tomato seedlings in Milwaukee?
Begin hardening off tomato seedlings May 7-10 in Milwaukee, about two weeks before transplanting. Start with 2-3 hours of filtered outdoor light, gradually increasing exposure over 10-14 days. Watch for Lake Michigan wind effects, which can damage tender seedlings even on warm days. Bring seedlings indoors if temperatures drop below 45°F during the hardening period.
What's the latest I can plant tomatoes in Milwaukee and still get a harvest?
The absolute latest transplant date for Milwaukee is June 10, and only for ultra-early varieties like Solanum lycopersicum 'Stupice' (60 days) or Solanum lycopersicum 'Early Girl' (62 days). This timing allows harvest beginning August 10-15, providing 6-7 weeks of production before September 30 frost. Later planting requires season extension methods or greenhouse growing to achieve meaningful harvests.
How do I protect tomatoes from Late Blight in Milwaukee?
Late Blight prevention in Milwaukee focuses on air circulation and moisture management. Space plants wider than normal, prune lower leaves for airflow, and avoid overhead watering. If Late Blight is reported in southeastern Wisconsin, harvest all fruit immediately and dispose of plants in garbage (not compost). The disease spreads rapidly via airborne spores during Milwaukee's cool, humid September nights.
Should I grow determinate or indeterminate tomatoes in Milwaukee?
Both work well in Milwaukee's Zone 5b climate, but each serves different purposes. Indeterminate varieties like Solanum lycopersicum 'Early Girl' and Solanum lycopersicum 'Cherokee Purple' provide extended harvests throughout Milwaukee's 139-day season. Determinate varieties concentrate their harvest, useful for preservation projects. Most home gardeners prefer indeterminates for continuous fresh tomato production from July through September.
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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.
