Growing Watermelon

Best Planting Times for Watermelons in Oregon

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

Oregon’s climate features a variety of conditions, including temperate coastal areas and drier eastern regions. With USDA Hardiness Zones ranging from 3b to 9b, watermelon cultivation can vary significantly across the state.

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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 Oregon, where conditions can fluctuate greatly, a greenhouse provides a stable environment for optimal watermelon development. Greenhouses extend the growing season, protect plants from extreme weather, and allow for year-round cultivation with proper climate control. This is particularly beneficial in regions where late frost or cooler nights can hinder outdoor growth.

Consider investing in a 10×12 FT Greenhouse priced at $1,199 to ensure your watermelons thrive in a controlled environment.
Greenhouse Image 1
Greenhouse Image 2
Check the latest price on Amazon.

Fertilizer

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

Average Last Frost Dates for Oregon’s Major Cities

CityAverage Last Frost Date
PortlandApril 28
EugeneMay 3
SalemMay 5
BendJune 10
MedfordApril 20
CorvallisMay 1
AshlandApril 15

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 Oregon:

Broccoli Planting in Oregon

Pumpkin Planting in Oregon

Tomato Planting in Oregon

Any questions on growing watermelons? Visit our forum to discuss: Growing Watermelons.

Starting Watermelon Indoors

In Oregon (Zone 8a), begin indoor watermelon seed starting between March 15 and April 15. 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 18-36 inches apart in rows with at least 6 feet between rows for optimal growth.

General Care and Maintenance

Watering

  • Provide consistent and deep watering to maintain evenly moist soil. Oregon’s moderate climate requires regular watering during dry spells 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. While Oregon’s coastal regions may have higher humidity, pest vigilance is essential.
  • Implement organic or integrated pest management methods to protect watermelon plants from pests and diseases.

Harvesting

  • Harvest watermelons when they exhibit a dull skin finish and the tendril closest to the fruit turns brown. Regular harvesting promotes continuous fruiting and ensures the best quality fruit.

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 organicrich organic matter that plants need to thrive.


In my garden I try to compost as mutch as possible, so I can mix in the nutrient ritch compost in my soil. I use both hot composting of food scraps and cold composting of all organic garden “waste”..
If you dont 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 you 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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