Luna Piena: The Winter Watermelon

Smoke rises from a mosquito coil while boisterous cicada fill the air with their song. The gentle sounds of a wind chime above them, a family gathers to eat refreshing, cool watermelon. A good old-fashioned Japanese summer scene. Summer means watermelon, and watermelon means summer! To most Japanese, watermelon is the summer fruit.

Watermelon: Only for summer?

However, there is one particular variety that turns this image on its head — many people no doubt surprised when they learn of the existence of a watermelon that is eaten in the wintertime. “Watermelon are delicious precisely because of the summer heat!” — so some may say, but they are missing out, if that is the stereotyped image they hold. Because, the premium-grade Luna Piena watermelon harvested in the winter in Kochi Prefecture is one that is abundantly sweet and flavorsome.

Yasu, home of winter watermelon

To learn more about the Luna Piena, let us venture to Kochi Prefecture on the island of Shikoku. Located in the prefecture’s east, Yasu is a coastal town that has been engaged in fishing and agriculture since ancient times. The Tei Harbor, built in the early Edo Period (1603-1868) and at the time the largest port in Japan, has long seen the coming and going of fishing boats and sailing ships. In the hills that rise above the port, agricultural pursuits have long taken advantage of the plateau-like topography and ample hours of sunshine.

Hironobu Ishihara of the JA Kochi Prefecture Yasu Branch explains that Yasu has historically been known for its sweet potatoes.

“We get a lot of sunshine here in Yasu, so there’s no problem growing foods that are native to warmer climates, such as watermelon or sweet potato. This is especially so in the Teiyama district where there is little groundwater and well-draining soil. The sweet potatoes suited for such a climate were grown here and shipped to urban areas such as Osaka and Edo (now Tokyo) and people apparently spoke highly of the ‘delicious sweet potatoes from Yasu,’” Ishihara points out.

“Research on cultivation methods, such as temperature control using straw or paper soaked in oil and so on, has been going on since long ago and these kinds of techniques have been used in the growing of watermelon.”

Carefully nurtured crops that take advantage of soil and climate: a tradition that has been passed down in Yasu through the ages to the present day.

<>bTre Frutta: Yasu’s premium grade fruit trio

When it comes to fruit grown in Yasu, there are three standouts. Known as ‘Tre Frutta’ (‘three fruits’ in Italian), they are the watermelon, musk melon (cantaloupe), and tomato. All are of exceptional quality with rich sweetness and umami flavors.

Yasu Emerald Melon

This high-quality melon made its market debut in May 1992 — the name is derived from the May birthstone. To bring out the exquisite sweetness, only one melon is harvested per vine. It is a carefully nurtured variety that is not only sweet, but also a beautiful sight to behold.

Yasu Fruit Tomato

This small tomato is grown to take full advantage of the long hours of sunshine found in Yasu. With a thin, crisp skin and a thick, juicy pulp, it is cultivated by restricting the amount of water it receives to increase sugar content and boost sweetness. While the yield is narrowed to about 1/3 of that of regular tomatoes, the result is a fruit that is exceedingly sweet.

Luna Piena Watermelon

Yasu’s premium-grade watermelon. The medium-sized fruit is harvested between late October and late March, while the large-sized type is picked between late April and late June. Watermelon that can be eaten through the winter — unique among watermelon grown in Japan.

The winter watermelon grown in a suspended cradle

In Japan, the prized Luna Piena is grown by just five producers, all in Yasu Town. One of those producers is Takamasa Matsumoto, a full-time farmer for the past 38 years and the JA Kochi Prefecture Kami District Horticultural Committee Watermelon Subcommittee Chairman.

“Of all the fruits, watermelon is one that particularly requires a lot of sun. That is why, in order for the fruit to receive the maximum amount of sunlight possible, we use what we call the ‘aerial suspension’ cultivation technique here in Yasu,” he explains. “Each watermelon is hung up in the air with string — like they are in their own cradle. Yasu gets a lot of sunshine and we make the most of that by cultivating the fruit like this to make sure they receive the maximum amount of rays from every direction.”

Growing watermelon aerially like this is rare, even in Japan; the method is said to have begun here in Yasu around 1967. The name ‘Luna Piena’ means “full moon” in Italian, given to the fruit due to the way each is carefully strung up, hanging in mid air like the full moon in the night sky.

“Luna Piena are grown so there is only one watermelon produced per plant. This of course means the harvest is reduced, but we get a more nutrient-dense fruit that is sweeter and more delicious. Yasu does not have a lot of open, flat areas, so large-scale production is difficult. If you can’t go for quantity, you go for high quality, nurturing each individual fruit by hand.”

Plunk! Plunk! The sound of a watermelon that’s ready to eat

The watermelons are ready for winter harvesting about 80 days after the seedlings are planted. After around the 65-day mark, Matsumoto goes about the cradled watermelons, tapping each one with his hand. This is how watermelons grown in Yasu have been checked to determine if they are ready for eating from long ago.

“When you tap on an immature one, you’ll hear a high tone — as the fruit matures, this tone gradually becomes lower. If there are any hollow areas inside, you hear this thick ‘thud’ sound — that’s not a good sign. But, if you get a clear, tight ‘plunk’ sound, it’s a sign that you have a delicious watermelon with well-compacted flesh on your hands. We producers do this even just before the fruit ships; we get together in the packing area and give the watermelons one more tap, just to make sure. Are there any defective ones? Are they at the right ripeness? From the time they start growing to the time they’re ready to ship, they are certainly well looked-after!”

A year’s worth of gratitude: watermelon as a gift

Hironobu Ishihara can still recall the very first time he tasted a Luna Piena. “It was completely different to any other watermelon I’d tasted before. I was just blown away by just how delicious it was! There was no ‘greenness’ about it and the umami flavors were amazing. Even after eating it all, I had this lingering aroma in my mouth. In compound investigations, it has been found that the Luna Piena has a high proportion of glutamic acid — that really ups the sweetness and umami. I remember being taken aback, wondering how I could be eating such an exquisite watermelon in the cold of winter!”

Since it is a rare type of watermelon that can be eaten in the winter months, Luna Piena is said to be much sought-after as a winter fruit gift. The Japanese year-end gift-giving tradition of oseibo is when gifts are presented as thanks to those who have done you a favor during the past year. In addition to sake and seafood, luxury fruit is often the gift of choice.

“Taste it just once. It’s amazingly delicious!” Takamasa Matsumoto says, brimming with confidence. “Unusual, right? Winter watermelon. I think there is virtually no place other than Yasu that produces them. After all: summer means ‘watermelon’ to most people. But, that’s not to say there isn’t demand in the winter. Many actually look forward each year to eating this watermelon in the colder months. People probably initially thought, ‘Winter watermelon? Well, that’s not going to taste that great, is it?’ But when they took a bite: ‘Wow! This is fantastic!’ We now have a lot of repeat customers.”

Evolution of the winter watermelon

When asked what the secret was to cultivating delicious watermelons, Matsumoto replies, “The growing conditions. Watermelons are quite delicate. You can’t overdo it with water or fertilizer — you must continually make adjustments, depending on the weather and temperature. The Luna Piena is particularly hard to grow during times when there are shorter sunlight hours in the day. But, that is precisely why I am immensely satisfied when I produce really good fruit.”

“I was born and raised here in Yasu and have eaten watermelon from a very young age. When I think back to my childhood, the watermelon just wasn’t that nice back then in comparison to nowadays! There’s no doubt cultivation techniques have evolved over the years since. It has been a continuous trial and error process in the pursuit of creating something truly delicious — I think we’re now at the point we can finally see the fruit of our efforts!”

Luna Piena: each grown with tender love and care in the town of Yasu. The result of the efforts of a small number of producers to overcome difficult growing conditions in the colder months to make a heavenly tasting watermelon. This coming winter, these farmers will again be striving to create an even sweeter, even more delicious fruit for us to savor.