How are square watermelons grown?

Square watermelons are grown by placing the developing fruit inside a transparent square box while it is still small and still on the vine. As the watermelon expands, it pushes outward against the rigid walls of the box and takes on the cube shape. The technique was developed in Zentsuji City in Kagawa Prefecture, Japan, where local farmers began producing them as a novelty around 1978. The growers have to time the harvest carefully — too late, and the fruit cracks the box; too early, and it doesn't fully fill the corners.

Are square watermelons edible?

Technically yes, but in practice no. Square watermelons are harvested while still green and unripe, before the fruit fully ripens and softens, so that they hold their shape and can be displayed without spoiling for several weeks. As a result, the flesh is generally hard and not particularly sweet. They are sold and bought as decorative gift objects — the equivalent of a high-end fruit basket as a corporate gift — rather than as fruit for eating.

How much does a square watermelon cost?

Retail prices for square watermelons in Japanese department stores typically range from about ¥10,000 to ¥30,000 for standard-grade fruit, with rare premium specimens going up to roughly ¥50,000. They appear on the market in the early summer gift season, primarily June through August, and are sold through department-store fruit counters such as Sembikiya and the depachika of Mitsukoshi, Isetan, and Takashimaya. Most production is still concentrated in Kagawa Prefecture.

Today I Learned

Japan, apparently, grows square watermelons as a luxury gift item — ¥10,000 to ¥50,000 each, not really meant to be eaten

Invented in Kagawa Prefecture in the late 1970s, square watermelons are grown in transparent boxes on the vine and sold as decorative gifts at department stores for ¥10,000–¥50,000.

Published 2026-05-01 · 2 min read · By Daichi

◇ A perfectly cube-shaped green watermelon with dark stripes, sitting on a paper-lined wooden gift box on a department-store fruit counter, with a price tag visible nearby

A watermelon that doesn’t roll

You walk past the fruit counter at a Tokyo department store in early July and see, behind glass, a green watermelon. The watermelon is a cube. It is sitting flat. It is not rolling anywhere. It has the same dark stripe pattern as a normal watermelon, but at the corners the stripes bend at exactly 90 degrees. The price tag, calmly: ¥18,000.

You ask the staff if it is real. They say yes, it is real, it was grown like that, and it is mostly meant to be looked at, not eaten. You nod, because at this point in Japan you have learned to nod, and you walk away.

The fact

The square watermelon (shikaku suika) is a luxury fruit product invented in Zentsuji City, Kagawa Prefecture, in the late 1970s — local farmers began producing them around 1978. They are grown by enclosing the developing fruit, while it is still small and on the vine, inside a transparent square box. As the watermelon expands, it presses outward against the rigid walls of the box and takes on a cube shape. By the time the fruit is mature enough to harvest, it has filled the cube.

Two important details that make the punchline work:

They are harvested before the fruit fully ripens, so the flesh is firm enough to hold the cube shape on a shelf for weeks. As a result, the inside is hard, pale, and not very sweet.
They are priced and sold as gift objects, not as produce. Standard-grade square watermelons retail at roughly ¥10,000–¥30,000, with premium specimens at department-store fruit counters reaching about ¥50,000.

The buyer base is corporate gifting, summer ochugen presents, and the same novelty-luxury market that supports ¥3,000 strawberries and ¥10,000 melons. Square watermelon production is small — a few hundred to a few thousand fruits per year, mostly still from Kagawa.

Why it works this way

A few forces stack:

Gifting culture is the engine. Japan’s two formal gift seasons — ochugen in mid-summer and oseibo in winter — drive a multi-billion-yen luxury fruit market. Square watermelons hit the ochugen window precisely.
The box is the product. The cube shape was first promoted as a practical innovation: it stacks in refrigerators and cargo holds without rolling. In practice, square watermelons are too valuable to ever go into a normal fridge. The “practical” framing is mostly marketing — what people are actually buying is novelty plus gift signaling.
Unripe is the feature. Because the fruit is harvested early to keep its shape, the inside isn’t really edible in the normal sense. This is openly acknowledged in product descriptions; the buyer knows.
Variation is doing the work too. Pyramid watermelons, heart-shaped watermelons, and human-face-shaped watermelons exist, also from Japan, also as gift objects. The square is just the most famous of a small genre.

Where to see them

Sembikiya, Tokyo Nihombashi — the original luxury fruit retailer, established 1834. Often stocks square watermelons during the early-summer gift season.
Mitsukoshi Ginza, Isetan Shinjuku, Takashimaya Nihombashi (depachika) — premium fruit counters where you can see them next to ¥10,000 melons.
Kagawa Prefecture (production region) — Zentsuji City and surrounding farms remain the primary source; some local fruit shops sell them at a lower markup than Tokyo.

Closing

In most countries, a watermelon is a snack. In Japan, it is occasionally a sculpture you give to your boss. Apparently, when you grow a fruit inside a glass box for a few months, what comes out is no longer really a fruit — it is a gift.