Red tomatoes

Best Planting Times for Tomatoes in Wisconsin

Planting MethodActivityRecommended Dates
Outdoor PlantingIndoor Seed StartingApril 1 – May 1
Transplant OutdoorsMay 15 – June 1
Greenhouse PlantingYear-roundAdjust planting based on temperature control in the greenhouse

Planting Conditions

Wisconsin has a humid continental climate, with cold winters and warm, humid summers. The state falls within USDA Hardiness Zones 3b to 5b, making the growing season relatively short and requiring careful timing for planting tomatoes.

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Useful Tools for Starting Tomatoes Indoors

Using the right tools can save you time and increase your success rate.

Seeds

Quality seeds lead to better germination and healthier plants. Starting with high-quality seeds gives your tomatoes the best chance to thrive from the very beginning.
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Browse Tomato Seeds on Amazon

Planting Trays

Planting trays help you organize your seedlings and ensure they have enough space to grow before you transplant them outdoors. This makes the process more efficient and increases the chances of strong, healthy plants.
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Grow Lights

Grow lights are essential if you don’t have enough natural sunlight. They provide your seedlings with the light they need to grow strong and healthy, even in less-than-ideal conditions.
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Seed Starting Soil

Using light, fine soil specifically designed for seed starting helps young roots establish quickly and promotes healthy growth. It’s an easy way to give your seedlings the best start possible.
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Greenhouse Growing

In Wisconsin, where the growing season can be shortened by cooler temperatures, a greenhouse is essential for extending the season. It allows you to start your tomato plants earlier in the spring and continue growing them well into the fall. With proper heating, you can protect your plants from frost and potentially grow tomatoes year-round.

Currently, the 8x10x7.5 FT Greenhouse is priced at $999. It’s a great investment for ensuring your tomatoes thrive all year round.
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Check the latest price on Amazon.

Fertilizer

Fertilizer is essential to provide your tomato plants with the nutrients they need for strong growth and a successful harvest.
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Other planting guides for Wisconsin:

Any questions on growing tomatoes? Visit our forum to discuss: Growing Tomatoes

Plant tomatoes outdoors approximately 1-2 weeks after the last frost when the soil has warmed sufficiently to support growth.

Average Last Frost Dates for Wisconsin’s Largest Cities

CityAverage Last Frost Date
MilwaukeeApril 30
MadisonMay 2
Green BayMay 7
KenoshaMay 1
RacineMay 2
AppletonMay 10
WaukeshaMay 3
Eau ClaireMay 11
OshkoshMay 9
JanesvilleMay 5

Please note: These dates are averages and can vary from year to year.

Starting Tomatoes Indoors

In cities like Milwaukee (Zone 5b), start tomato seeds indoors from April 1 to May 1. This timing ensures that seedlings are ready for outdoor transplanting from mid-May to early June, once the risk of frost has passed.

Transplanting Tomato Seedlings

Transplant seedlings outdoors from May 15 to June 1, ensuring soil temperatures are consistently above 50°F. Space seedlings 24-36 inches apart in rows at least 36 inches apart to allow for good air circulation and sunlight exposure.

General Care and Maintenance

Watering:

  • Water deeply and consistently to maintain evenly moist soil. Wisconsin’s warm summers can dry out the soil quickly, so regular watering is essential.
  • Water at the base of the plants to prevent wetting the foliage, reducing the risk of fungal diseases.

Fertilizing:

  • Apply a balanced fertilizer at planting and again when the first fruits begin to set. Adding compost to the soil before planting can improve fertility and soil structure.

Pest and Disease Management:

  • Monitor for common pests like aphids, cutworms, and tomato hornworms. The humid climate can also encourage fungal diseases, so vigilance is necessary.
  • Use organic or integrated pest management strategies to protect your plants from pests and diseases.

Harvesting Tomatoes:

  • Harvest tomatoes when they are fully colored and firm. Regular harvesting during Wisconsin’s short summer months helps maintain fruit quality and prevents overripening.
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