How to Grow Japanese Watermelon: The Ultimate Guide for Bumper Harvests

Growing your own Japanese watermelon can be a rewarding experience, offering you a taste of exotic sweetness and the satisfaction of nurturing a unique fruit from seed to harvest. While these watermelons may appear challenging to grow, with the right knowledge and techniques, you can cultivate these intriguing fruits in your backyard. This comprehensive guide will walk you through the process of growing Japanese watermelon, from selecting the right variety to harvesting plump, square fruits.

Understanding Japanese Watermelon Varieties

Japanese watermelons, also known as “square watermelons,” are a fascinating variety of watermelon known for their distinctive shape. This unique shape is not a natural occurrence but a result of growing the fruit within a mold during its development. While the square shape is intriguing, it’s important to remember that the actual flavor and sweetness of the watermelon are not affected by its shape.

When choosing a Japanese watermelon variety, consider the following factors:

• Size and shape: Japanese watermelons come in various sizes, ranging from small, personal-sized fruits to larger varieties suitable for sharing.
• Maturity time: Some varieties mature faster than others, so choose a variety that aligns with your growing season.
• Flavor profile: Japanese watermelons are known for their sweet and refreshing taste, but some varieties may have a slightly different flavor profile.

Selecting the Right Location and Soil

Japanese watermelons thrive in warm climates with plenty of sunshine and well-drained soil. Choose a sunny spot in your garden that receives at least six hours of direct sunlight daily.

The soil should be loose and fertile, with a pH between 6.0 and 6.5. Before planting, amend the soil with compost or aged manure to improve drainage and nutrient content.

Planting Japanese Watermelon Seeds

Japanese watermelon seeds can be started indoors or directly sown outdoors.

Starting Seeds Indoors:

• Sow seeds 2-3 weeks before the last frost date.
• Use seed trays or individual pots filled with seed starting mix.
• Plant seeds 1/2 inch deep and space them 2-3 inches apart.
• Keep the soil consistently moist and warm.
• Transplant seedlings outdoors after the last frost, when they have developed 2-3 true leaves.

Direct Sowing:

• Sow seeds directly in the garden after the soil has warmed to at least 70°F.
• Plant seeds 1/2 inch deep and space them 2-3 feet apart.
• Water thoroughly after planting.

Providing Adequate Water and Sunlight

Watermelons require consistent moisture, especially during the early stages of growth. Water deeply and regularly, ensuring the soil is moist but not soggy.

As the vines mature, they will need more water. During hot and dry weather, watermelons may require daily watering.

Japanese watermelons need plenty of sunlight to thrive. Ensure they receive at least six hours of direct sunlight daily.

Maintaining a Healthy Watermelon Vine

• Fertilize: Watermelons are heavy feeders and benefit from regular fertilization. Apply a balanced fertilizer every 2-3 weeks, following the manufacturer’s instructions.
• Mulch: Apply a layer of mulch around the base of the vines to help retain moisture and suppress weeds.
• Trellising: While not mandatory, trellising can help support the vines and improve air circulation, reducing the risk of diseases.
• Pest Control: Monitor the vines regularly for pests such as aphids, spider mites, and squash bugs. Use organic pest control methods or insecticidal soap if necessary.

Shaping the Watermelon into a Square

The distinctive square shape of Japanese watermelons is achieved through a process called “molding.” Here’s how it works:

• Select a mold: Choose a mold made of sturdy material like wood or plastic. The mold should be approximately the size and shape you desire for your watermelon.
• Place the mold: When the watermelon is about the size of a tennis ball, place the mold around the fruit.
• Secure the mold: Secure the mold in place using twine or straps.
• Continue to grow: The watermelon will grow within the mold, taking on its shape.

Harvesting and Storing Japanese Watermelon

Japanese watermelons are typically ready for harvest 80-100 days after planting. Here are some signs the fruit is ripe:

• Color: The rind should be a deep green color.
• Sound: When you tap the watermelon, it should produce a dull, hollow sound.
• Stem: The stem should be dry and brown.

Once harvested, store Japanese watermelons in a cool, dry place for up to a week.

The Sweet Success of Homegrown Japanese Watermelon

Growing Japanese watermelon can be a fun and rewarding experience. By following these steps, you can enjoy the unique flavor and shape of this exotic fruit grown right in your own backyard. Remember to be patient, observant, and attentive to your plants’ needs, and you’ll be rewarded with a bountiful harvest of sweet, square watermelons.

Quick Answers to Your FAQs

Q: Can I grow Japanese watermelon in a container?

A: Yes, Japanese watermelons can be grown in containers, but they will need a large container with a diameter of at least 18 inches.

Q: What are the benefits of growing square watermelons?

A: While the square shape is primarily for aesthetics, it can make it easier to store and transport the fruit.

Q: Can I use any type of mold to shape the watermelon?

A: It’s best to use a mold specifically designed for shaping watermelons, as it will be durable enough to withstand the weight of the growing fruit.

Q: What are some common problems that can affect Japanese watermelons?

A: Common problems include fungal diseases, pests, and insufficient watering.

Q: How long does it take for a Japanese watermelon to mature?

A: Japanese watermelons typically mature in 80-100 days after planting.