Satsumaimo: Sweet Potatoes Here, There, and Everywhere

Satsumaimo Fairs Attract Crowds

Sweet potatoes, called satsumaimo in Japanese, are all the rage in Japan. The autumn harvest brought with it sweet potato-themed festivals galore, with fans of the tuber flocking to satsumaimo “expos” in Osaka, Kanagawa, Shimane, Aichi, and other prefectures around Japan. Shizuoka held its second such event in early November after an immensely popular spring fair in March. The events highlight all things satsumaimo, from deliciously sweet roasted yakiimo to mouth-watering desserts made from sweet potatoes.

Kawasaki in Kanagawa Prefecture held its own “Super Spud Festa” in November, a free, four-day event that featured satsumaimo-themed workshops on harvesting and grading sweet potatoes along with abundant shopping opportunities, including 15 shops from around the country offering satsumaimo sweets. The organizers made it clear that the boom in sweet potato confections is not a flash in the pan; satsumaimo are here to stay as an ingredient in pies, cakes and other sweets.

Crowds gather at the Satsumaimo Expo held in summer in Saitama. (Courtesy Satsumaimo Festival Organizing Committee)

Mainland Import

Sweet potatoes boast a long and important history. According to Japan’s agriculture ministry website, they originated in tropical regions of Central America centering on what today is Mexico and began to be cultivated in the Central Andes from around 800 to 1000 BCE. Sweet potatoes traveled with Christopher Columbus from the New World to Europe around the end of the fifteenth century, but unfavorable climatic conditions on the continent made them hard to grow there. However, they spread worldwide when colonizers later introduced the tubers in Africa, India, and Southeast Asia.

Sweet potatoes first appeared in the Ryūkyū kingdom in present-day Okinawa around the 1600s, reaching the islands via China through trade channels. From there they spread northward to Satsuma (today’s Kagoshima Prefecture), whence came the name satsumaimo, meaning “Satsuma potato.” Sweet potatoes are sometimes also called karaimo, with kara indicating provenance from China, or kansho, their name in Chinese.

Consumption of sweet potatoes grew as their cultivation spread throughout Japan, and satsumaimo have enjoyed several boom periods through history. According to Hashimoto Ayuki, who heads the promotional Satsumaimo Ambassador Association, farming of sweet potatoes received a boost during the Edo period (1603–1868) when eighth shōgun Tokugawa Yoshimune, moved by a work by scholar of Dutch studies Aoki Kon’yō , ordered the starchy tubers to be grown as a foodstuff to be used in times of famine.

Roasted satsumaimo, called yakiimo, set off the first boom when street vendors began offering the treats in Edo (today Tokyo) in 1793. Following the inauguration of the new Meiji government in 1868, Tokyo’s population rapidly grew and a second boom ensued that was driven by the popularity of sweet potatoes as an affordable food. The emergence of Western-style confectionery in the 1920s pushed satsumaimo into the background, but they enjoyed a third resurgence in the 1950s with the arrival of ishiyakiimo, sweet potatoes roasted on hot stones, sold from handcarts drawn by vendors. “People enjoyed the convenience of being able to buy roasted sweet potatoes near their homes,” Hashimoto says, “and demand boomed.”

Few yakiimo sellers make the rounds in neighborhoods nowadays, but many supermarkets and convenience stores have had success selling roasted sweet potatoes. The fourth and most recent boom was sparked when electric roasters came into the picture around 2010 and has been buffeted along by the appearance of new types of sweet potatoes, particularly the sweet, creamy Annō-imo variety.

The Many Personalities of Satsumaimo

The diverse tastes of consumers has spurred the development of a range of new varieties of satsumaimo. According to the agriculture ministry, the most commonly cultivated type in Japan today is Beniharuka, which has a creamy consistency when roasted. Beniazuma, with a drier, flaky mouthfeel, is prevalent in the Kantō region. Meanwhile, Kōkei #14, which offers a well-balanced combination of flakiness and creaminess, is grown extensively in Kansai and southern Kyūshū. Other varieties which are offshoots of Kōkei #14 include local brands Gorōjima Kintoki (Ishikawa), Naruto Kintoki (Tokushima), Miyazaki Beni (Miyazaki), and Benisatsuma (Kagoshima).

The Annō-imo variety, which sparked the latest satsumaimo boom, arose on the island of Tanegashima in Kagoshima from sweet potatoes brought from Indonesia. Amid growing popularity, Annō-imo started being widely marketed, and two varieties were registered in 1998: Annōbeni, with reddish-brown skin, and the amber-colored Annōkogane. In March 2022, both were registered as Tanegashima Annō-imo and given the geographical indicator designation, a mark assigned by the government to protect regional brands.

Amid growing demand for sweet potatoes, Hokkaidō has rapidly increased its production volume of satsumaimo. Production area in 2023 stood at 100 hectares, 7.1 times what it was 10 years earlier, and the year’s harvest came to 1,870 tons, 6.7 times what it was the previous decade. Climate change has played a part in the increase by making the cooler climate of the northernmost of Japan’s four main islands more suitable for growing sweet potatoes. Satsumaimo have also been newly added to the government’s list of strategic crops, which is likely to increase cultivation even more.

Japan-grown satsumaimo are increasingly finding their way to overseas markets as well. Trade figures from the Ministry of Finance list the value of sweet potato exports in 2023 at ¥2.9 billion, up 9.4 times what it was 10 years ago. Sweet potatoes have climbed to third place behind strawberries and nagaimo (Chinese yam), showing its importance as an export crop. Hong Kong, Singapore, and Thailand account for nearly 90% of exports, with shipments to the latter being on the rise as Japanese growers eye the Asian market as a top region for export growth.

Star Product

The enduring popularity of satsumaimo has been strongly supported by yakiimo, one of the best-loved sweet potato options. Summit, a supermarket chain with stores in Tokyo, Kanagawa, Chiba, and Saitama, sells roasted Annō-imo in season along with varieties such as Beniharuka, Silksweet, Naruto Kintoki, and Gorōjima Kintoki. Each outlet also has signage with the hours at which freshly roasted sweet potatoes will be ready for sale. A Summit public relations officer notes that many customers are drawn to its stores by yakiimo, with positive reviews on social media helping spread the word among sweet potato fans.

A supermarket counter selling a selection of yakiimo. (Courtesy Summit)

While freshly roasted sweet potatoes are a winter mainstay, new options like chilled yakiimo are also attracting attention as a summer treat. Convenience store chain FamilyMart sells a cool version using Beniharuka that have been stored and matured for over three months. The company says the product has won the hearts of customers for its mild natural sweetness and contrasting slight bitterness of the charred skin. Getting fully into the satsumaimo swing, FamilyMart hosted a sweet potato digging event in September as part of its autumn sales campaign.

Confectionery makers have also been adding sweet potato-themed products to their lineups. Mie-based food manufacturer Imuraya, for instance, offers a mini sweet potato yōkan, a type of jellied sweet, made from whole Beniharuka tubers, while snack maker Matsunaga Seika has concocted a version of its flagship line of Shiruko Sando cracker with a filling made from Kagoshima-grown Annō-imo.

Confectionery items featuring satsumaimo. (© Kume Chikuma)

Sweet potatoes are also increasingly on the menu at cafés. Tully’s Coffee Japan sells a special latte and other seasonal beverages showcasing Japan-grown sweet potatoes. Getting a head start on the season, shops offered a lineup of sweets and other satsumaimo-flavored products starting from August and September.

Hashimoto of the Satsuma Ambassador Association says that continuing development and the launch of new satsumaimo products has enabled consumers to enjoy sweet potatoes year-round rather than just during the autumn harvest period. He says that even once the current boom cools down, he expects sweet potatoes will retain their appeal as snacks and mealtime treats.

(Originally published in Japanese. Banner photo: Roasted Beniharuka sweet potatoes. © Pixta.)