Growing Watermelon

Best Planting Times for Watermelons in Minnesota

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

Planting Conditions

Watermelon Planting Conditions

Minnesota’s climate can be challenging for watermelon cultivation due to short growing seasons and cooler temperatures. Understanding the best planting dates and methods is essential to ensure healthy watermelon production.

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Useful Tools for Starting Watermelons 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 watermelons the best chance to thrive from the very beginning.
5 pack of different Melon Seeds
Browse Watermelon 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.
Planting Trays Image
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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.
Grow Lights Image
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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.
Seed Starting Soil Image
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Greenhouse Growing

In Minnesota, the fluctuating temperatures and shorter growing seasons can hinder watermelon growth. A greenhouse can provide a stable environment for optimal development. Greenhouses help extend the growing season, protect plants from harsh weather, and allow for earlier planting with proper climate control.

Consider investing in a 10×12 FT Greenhouse for improved growth conditions for your watermelons.
Greenhouse Image 1
Greenhouse Image 2
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Fertilizer

For optimal watermelon growth in Minnesota, supplementing with fertilizer can help ensure abundant and healthy harvests. Quality fertilizer restores nutrients in the soil and promotes vigorous plant growth.
Fertilizer Image
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Plant watermelons outdoors in Minnesota approximately 1-2 weeks after the last spring frost date, ensuring the soil is warm enough for optimal growth.

Average Last Frost Dates for Minnesota’s Major Cities

CityAverage Last Frost Date
MinneapolisMay 10
Saint PaulMay 12
RochesterMay 17
DuluthMay 25
BloomingtonMay 11
Brooklyn ParkMay 15
PlymouthMay 14
EaganMay 16
Coon RapidsMay 18
LakevilleMay 24

Disclaimer: Frost dates are average estimates, and actual conditions may vary. It is recommended to monitor local forecasts and adapt planting decisions accordingly.

Other planting guides for Minnesota:

Broccoli Planting in Minnesota

Pumpkin Planting in Minnesota

Tomato Planting in Minnesota

Any questions on growing cucumbers? Visit our forum to discuss: Growing Cucumbers.

Starting Watermelon Indoors

In Minnesota (Zone 4a to 4b), begin indoor watermelon seed starting between April 15 and May 1. This timeline ensures healthy seedlings ready for outdoor transplantation starting from late May to early June once the risk of frost has passed.

Transplanting Watermelon Seedlings

Transplant watermelon seedlings outdoors from June 1 to June 15, ensuring the soil has warmed above 70°F consistently. Space the seedlings 24-36 inches apart in rows with at least 4-6 feet between rows for optimal growth.

General Care and Maintenance

Watering

  • Provide consistent and deep watering to maintain evenly moist soil. Minnesota’s varying rainfall necessitates regular watering during dry periods to prevent soil dryness.
  • Water at the base of plants to avoid leaf wetness, reducing the risk of fungal diseases.

Fertilizing

  • Apply a balanced fertilizer during planting and when the first fruits start forming. Incorporating compost before planting can enhance soil fertility and structure.

Pest and Disease Management

  • Regularly monitor for common pests like aphids, cucumber beetles, and powdery mildew. Minnesota’s seasonal changes may introduce various pests, making vigilance essential.
  • Implement organic or integrated pest management methods to protect watermelon plants from pests and diseases.

Harvesting

  • Harvest watermelons when they reach the desired size and the skin turns dull, indicating ripeness. Regular harvesting promotes continuous fruiting and prevents overripening.

The importance of good soil

Before starting to grow it is important to take a step back and find the condition of the soil in your garden, The optimal soil is a blend that includes the mineral-rich dirt along with organic rich organic matter that plants need to thrive.


In my garden I try to compost as much as possible, so I can mix in the nutrient rich compost in my soil. I use both hot composting of food scraps and cold composting of all organic garden “waste”..
If you don’t have the time or space for composting, it is possible to get compost ready to use in garden centers and Community Composting.
You can read more on Community Composting here: https://www.epa.gov/sustainable-management-food/community-composting

If you are uncertain of the quality of your soil, you can get easy to use soil tests at Amazon for 17 dollars. Check latest prices here: Soil testing kit.

Also remember to check out how much sunlight your growing area gets, and that the rain drains well. If you treat your soil well and plan your crops according to your climate you will succeed with any plant you want.

The satisfaction when you harvest your own produce is well worth the time you put in 🙂

BeeJay
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