The Secret Behind Japan’s Wintry Strawberries

MINOH, Japan — Strawberry shortcake. Strawberry mochi. Strawberries à la mode.

These may sound like summertime delights. But in Japan, the strawberry crop peaks in wintertime — a chilly season of picture-perfect berries, the most immaculate ones selling for hundreds of dollars apiece to be given as special gifts.

Japan’s strawberries come with an environmental toll. To recreate an artificial spring in the winter months, farmers grow their out-of-season delicacies in huge greenhouses heated with giant, gas-guzzling heaters.

“We’ve come to a point where many people think it’s natural to have strawberries in winter,” said Satoko Yoshimura, a strawberry farmer in Minoh, Japan, just outside Osaka, who until last season burned kerosene to heat her greenhouse all winter long, when temperatures can dip well bellow freezing.

But as she kept filling up her heater’s tank with fuel, she said, she started to think: “What are we doing?”

Fruits and veggies are grown in greenhouses all over the world, of course. The Japan strawberry industry has carried it to such an extreme, however, that most farmers have stopped growing strawberries during the far less lucrative warmer months, the actual growing season. Instead, in summertime Japan imports much of its strawberry supply.

It’s an example of how modern expectations of fresh produce year round can require surprising amounts of energy, contributing to a warming climate in return for having strawberries (or tomatoes or cucumbers) even when temperatures are plunging.

Up until several decades ago, Japan’s strawberry season started in the spring and ran into early summer. But the Japanese market has traditionally placed a high value on first-of-the-season or “hatsumono” produce, from tuna to rice and tea. A crop claiming the hatsumono mantle can bring many times normal prices, and even snags fevered media coverage.

As the country’s consumer economy took off, the hatsumono race spilled over into strawberries. Farms started to compete to bring their strawberries to market earlier and earlier in the year. “Peak strawberry season went from April to March to February to January, and finally hit Christmas,” said Daisuke Miyazaki, chief executive at Ichigo Tech, a Tokyo-based strawberry consulting firm.

Now, strawberries are a major Christmas staple in Japan, adorning Christmas cakes sold across the country all December. Some farmers have started to ship first-of-the-season strawberries in November, Mr. Miyazaki said. (Recently, one picture perfect Japanese-branded strawberry, Oishii (which means “delicious”), has become TikTok-famous, but it is grown by a U.S. company in New Jersey.)

Japan’s swing toward cultivating strawberries in freezing weather has made strawberry farming significantly more energy intensive. According to analyses of greenhouse gas emissions associated with various produce in Japan, the emissions footprint of strawberries is roughly eight times that of grapes, and more than 10 times that of mandarin oranges.

“It all comes down to heating,” said Naoki Yoshikawa, a researcher in environmental sciences at the University of Shiga Prefecture in western Japan, who led the produce emissions study. “And we looked at all aspects, including transport, or what it takes to produce fertilizer — even then, heating had the biggest footprint.”

Examples like these complicate the idea of eating local, namely the idea embraced by some environmentally conscious shoppers of buying food that was produced relatively close by, in part to cut down on the fuel and pollution associated with shipping.

In general, though, transportation of food has less of a climate impact than the way in which it is produced, said Shelie Miller, a professor at the University of Michigan who focuses on climate, food and sustainability. One study found, for example, that tomatoes grown locally in heated greenhouses in the Britain had a higher carbon footprint compared to tomatoes grown in Spain (outdoors, and in-season), and shipped to British supermarkets.

Climate-controlled greenhouses can have benefits: They can require less land and less pesticide use, and they can produce higher yields. But the bottom line, Professor Miller said, is that “it’s ideal if you can eat both in-season, and locally, so your food is produced without having to add major energy expenditures.”

In Japan, the energy required to grow strawberries in winter hasn’t proven to be just a climate burden. It has also made strawberry cultivation expensive, particularly as fuel costs have risen, hurting farmers’ bottom lines.

Research and development of berry varieties, as well as elaborate branding, has helped alleviate some of those pressures by helping farmers fetch higher prices. Strawberry varieties in Japan are sold with whimsical names like Beni Hoppe (“red cheeks”), Koinoka (“scent of love”), Bijin Hime (“beautiful princess.”) Along with other pricey fruit like watermelons, they are often given as gifts.

Tochigi, a prefecture north of Tokyo that produces more strawberries than any other in Japan, has been working to tackle both climate and cost challenges with a new variety of strawberry it is calling Tochiaika, a shortened version of the phrase, “Tochigi’s beloved fruit.”

Seven years in the making by agricultural researchers at Tochigi’s Strawberry Research Institute, the new variety is larger, more resistant to disease, and produces a higher yield from the same inputs, making growing them more energy efficient.

Tochiaika strawberries also have firmer skin, cutting down on the number of strawberries that get damaged during transit, thereby reducing food waste, which also has climate consequences. In the United States, where strawberries are grown mostly in warmer climates in California and Florida, strawberry buyers discard an estimated one-third of the crop, partly because of how fragile they are.

And instead of heaters, some farmers in Tochigi use something called a “water curtain,” a trickle of water that envelopes the outside of greenhouses, keeping temperatures inside constant, though that requires access to ample groundwater. “Farmers can save on fuel costs, and help fight global warming,” said Takayuki Matsumoto, a member of the team that helped develop the Tochiaika strawberry. “That’s the ideal.”

There are other efforts afoot. Researchers in the northeastern city of Sendai have been exploring ways to harness solar power to keep the temperature inside strawberry greenhouses warm.

Ms. Yoshimura, the strawberry farmer in Minoh, worked in farming a decade before deciding she wanted to do away with her giant industrial heater in the winter of 2021.

A young mother of one, with another on the way, she had spent much of the lockdown days of the pandemic reading up on climate change. A series of devastating floods in 2018 that wrecked the tomato patch at the farm she runs with her husband also awakened her to the dangers of a warming planet. “I realized I needed to change the way I farmed, for the sake of my kids,” she said.

But in mountainous Minoh, temperatures can dip to below 20 degrees Fahrenheit, or about minus 7 Celsius, levels at which strawberry plants would normally go dormant. So she delved into agricultural studies to try to find another way to ship her strawberries out during the lucrative winter months, while not using fossil fuel heating.

She read that strawberries sense temperatures via a part of the plant known as the crown, or the short thickened stem at the plant’s base. If she could use groundwater, which generally stays at a constant temperature, to protect the crown from freezing temperatures, she wouldn’t have to rely on industrial heating, she surmised.

Ms. Yoshimura fitted her strawberry beds with a simple irrigation system. For extra insulation at night, she covered her strawberries with plastic.

She stresses that her cultivation methods are a work in progress. But after her berries survived a cold snap in December, she took her industrial heater, which had remained on standby at one corner of her greenhouse, and sold it.

Now, she’s working to gain local recognition for her “unheated” strawberries.  “It would be nice,” she said, “if we could just make strawberries when it’s natural to.”