Growing Watermelon

Best Planting Times for Watermelons in Hawaii

Planting MethodActivityRecommended Dates
Outdoor PlantingDirect SowingFebruary 1 – March 31
Transplanting SeedlingsApril 1 – April 15
Greenhouse PlantingYear-roundAdjust planting based on temperature control in the greenhouse

Planting Conditions

Watermelon Planting Conditions

Hawaii’s tropical climate is ideal for watermelon cultivation, with warm temperatures and ample sunlight throughout the year. The state’s USDA Hardiness Zones generally range from 10a to 11b, providing a conducive growing environment.

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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 can provide supplemental lighting if necessary, ensuring that your watermelon seedlings receive adequate light for optimal growth. This can be particularly useful in areas with limited natural sunlight.
Grow Lights Image
Check out Grow Lights on Amazon

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 Hawaii, where temperatures remain warm year-round, using a greenhouse provides a few notable benefits. It protects watermelon plants from extreme weather events like heavy rains and strong winds while allowing for better pest and disease control. Additionally, a greenhouse can help extend the growing season, enabling you to start earlier and harvest later.

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 Hawaii, 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 Hawaii approximately 1-2 weeks after the last frost date, ensuring the soil is warm enough for optimal growth.

Average Last Frost Dates for Hawaii’s Major Islands

IslandAverage Last Frost Date
Hawaii IslandNone
MauiNone
OahuNone
KauaiNone

Disclaimer: Hawaii typically does not experience frost, making it a prime location for year-round crops like watermelon. However, it is always good to monitor local weather conditions.

Other Planting Guides for Hawaii:

Kale Planting in Hawaii

Pumpkin Planting in Hawaii

Tomato Planting in Hawaii

Any questions on growing watermelons? Visit our forum to discuss: Gardening Forum.

Starting Watermelon Indoors

In Hawaii, beginning indoor watermelon seed starting is recommended from January 1 to February 15. This timeline ensures robust seedlings that are ready for outdoor transplantation starting from mid-February to early March, taking advantage of Hawaii’s warm climate.

Transplanting Watermelon Seedlings

Transplant watermelon seedlings outdoors from March 1 to March 15, making sure the soil temperature is consistently above 70°F for optimal growth. Space the seedlings 3-4 feet apart in rows that are at least 6-8 feet apart to allow for sprawling.

General Care and Maintenance

Watering

  • Watermelons need consistent moisture, especially during flowering and fruit development. Avoid letting the soil dry out completely.
  • Water at the base of the plants to prevent overhead watering, which can encourage diseases in warm, humid conditions.

Fertilizing

  • Use a balanced fertilizer at planting and again during mid-growth. Local compost or organic fertilizers can help enhance soil nutrients and promote healthy growth.

Pest and Disease Management

  • Regularly inspect for pests such as aphids, spider mites, and cucumber beetles. Hawaii’s warm climate may attract various pests, so vigilance is key.
  • Utilize organic pest management methods, including companion planting and introducing beneficial insects to protect your watermelon plants.

Harvesting

  • Harvest watermelons when the tendril closest to the fruit has turned brown, and the bottom spot is a creamy yellow color. Regularly checking for ripeness will ensure the best flavors and textures.

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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