“Banpeiyu”: The Citrus Connecting Taiwan and Kumamoto

The Massive Fruit of Kumamoto

The banpeiyu is a white-fleshed variety of pomelo (Citrus maxima) grown in both Kumamoto Prefecture and Taiwan. The chief characteristic of this fruit is its massive size. Mature ones average around 20 centimeters in diameter and can weigh around 2 kilograms, making them as large as a child’s head. The largest can reach over 25 centimeters across.

Like other pomelos, they do not produce much juice and have pleasantly firm flesh. They also have outstanding shelf life and can be stored for around a month after harvesting. Fruit is usually best enjoyed as fresh as possible, but banpeiyu actually get better with some time resting after harvest. They are quite aromatic, and when the fruit approaches its peak, it fills the room with a gorgeous sweet and sour scent.

Kumamoto accounts for 96% of Japan’s entire banpeiyu harvest, and the southern Kumamoto city of Yatsushiro is a particular specialist in the fruit, which is harvested in winter and has become a popular seasonal gift.

The logo of the Hisatsu Orange Railway, which connects Kumamoto’s Yatsushiro with Sendai in Kagoshima Prefecture. The biggest of the fruit pictured is a pomelo. (© Katakura Yoshifumi)

Agricultural Scientist Shimada Yaichi

Tracking down the history of this fruit revealed a surprising link between Kumamoto and Taiwan.

The banpeiyu story cannot be told without a discussion of the botanist Shimada Yaichi (1884–1971). Shimada was an agricultural scientist for the Japanese appointed Government-General of Taiwan and lived there for 40 years. He discovered some 38 species and varietals of plantn Taiwan, and established cultivation of the ponkan (Citrus poonensis, or “honey orange”) in the north of the island. He also started cultivating Casuarina equisetifolia, or coastal she-oak, as a coastal windbreak. He is one of the most important figures in Taiwan’s agricultural history.

Shimada was born in Yatsushiro, Kumamoto Prefecture, and graduated from the Kumamoto Agricultural College. He then worked at a botanical disease research center under the botanist Kawakami Takiya, a teacher at his university. Kawakami also worked extensively in Taiwan and was the first head of the National Taiwan Museum,

Shimada was hired in 1904 by the Governor-General of Taiwan’s Office to work at an agricultural experimental farm, tasked with rice paddy and sweet potato farm trials and climate observations. He was put in charge of surveying Taiwan’s main agricultural produce the next year, when he began walking the whole of the island. He then had a post in the agricultural affairs division under the Government-General and became a general agricultural statistician.

Shimada began an agricultural inspection tour of Southeast Asia in 1919, visiting areas like British Malaya, Burma, Siam (now Thailand), and French Indochina (now Vietnam). He encountered the banpeiyu at a dinner on board the ship and was enthralled by the flavor. He quickly went to work tracking it down and received some seedlings during an observation tour of a Saigon botanical garden, taking them back to Taiwan.

Shimada Yaichi spent years working on agricultural development in Taiwan. He is also known for his study of ponkan and tankan citrus. Picture from Shinchikushū taikan (Survey of Shinchiku Prefecture)

Competing with Native Pomelos

When Shimada returned to Taiwan, he chose the horticultural research center in Shilin outside of Taipei for testing. He conducted study after study, but it was the scientist Sakurai Yoshijirō of the government’s central research center who made a breakthrough. An expert on tropical fruit trees who contributed greatly to Taiwan’s fruit tree cultivation, Sakurai studied the five seedlings that Shimada had brought to Taiwan to find the fruit’s characteristics and find a suitable cultivation method for the local climate.

Sakurai wrote about the difficult road to establishing cultivation, like how at first, the ripe fruit grew so big that the trunks broke, or how the thorny branches damaged the growing fruit.

It takes a long time for ordinary pomelo trees to reach fruiting age, usually around six or seven years, and it takes a decade at least to achieve a proper harvest. Banpeiyu are no different in this respect, but one difference is that they ripen somewhat later than other pomelos. That means their season does not overlap with other fruits’ shipping seasons.

The banpeiyu harvest starts from December, around when the season is wrapping up for the traditional Taiwanese pomelo, and lasts until the next spring. This lateness is part of the name, as the first character, 晩 (ban) means “evening” or “late,” and was chosen by Sakurai in 1926.

The Shilin Horticultural Reseach Branch of the Central Research Institute, Office of the Governor-General of Taiwan, is now the Shilin Residence Park. It was opened to the public in 1996 as a recreational spot. (© Katakura Yoshifumi)

Nitabe Inazō and Industrial Agriculture

Agricultural research was an active pursuit during Japan’s control of Taiwan. The new territory was quite different from Japan in terms of its soil and climatic zone. Naturally, that meant that research across a wide range of areas was needed to find agriculture that worked for Taiwan.

Specifically, research focused on farming methods, introducing new varieties, improving existing varieties, selecting ideal fertilizers, and pest control, but the two main axes were methods to increase production stability and improve profitability. This began with the educator and statesman Nitobe Inazō, who worked in the early years of the twentieth century as an agronomist.

Nitobe was tasked by the director of Taiwan’s Civil Administration, Gotō Shinpei, with producing proposals for agricultural development in Taiwan. He was appointed to the Government-General’s Agricultural Affairs Office in 1901, and in September that year he presented his plan for sugar industry improvements. The paper positioned sugar refining as a strategic industry and proposed its development as a matter of policy.

This is an example of Nitobe’s theory of parallel development in agriculture, commerce, and industry, in which agriculture is part of national industrial policy and actively industrialized after publicly funded research. The next step was to commercialize agriculture to gain foreign currency. The core of this industrialization in Taiwan was sugar, but fruit was treated in a similar fashion.

When it came to banpeiyu, publicly funded research led to stable production for intensive cultivation. Looking to the future, officials also began considering transporting and exporting the fruit to Japan’s mainland and outlying islands. In other words, development of banpeiyu and other fruits followed Nitobe’s plan.

Officials made many observation visits to the South Pacific, particularly from the early Taishō period (1912–26) onward, looking for fruit. In addition to the banpeiyu that Shimada discovered in Southeast Asia, researchers also began working on mangoes, pineapples, and oranges, among others. These trips lasted about half a year, a sign of the great hopes placed in them by the Government-General.

Pomelos are called youzi in Taiwan. They grow well in mildly alkaline soils and are weak against acidity. The Madou district of Tainan, Taiwan, is a famous producer. (© Katakura Yoshifumi)

Taking Root in Southern Kumamoto

From there, banpeiyu steadily gained favor and cultivation spread acroess the flatlands of southern Taiwan. Farmers liked that the trees were hardy and resistant to both flooding and drought. And, since they drew high prices and produced lots of fruit, they were also profitable. In 1935, Volume 10 of the Academic Society of Japan Report noted that the number of saplings had reached 200,000 in 1933, and had covered important sections of southern Taiwan.

The fruit gained favor not only for its flavor but its shelf life, as well. In fact, the longer it was stored the better the sweet and sour flavors melded, allowing consumers to decide the best time to eat for themselves.

The banpeiyu that Shimada and Sakurai had worked so hard to establish in Taiwan finally came to the Japanese mainland in 1930. Citruses usually do not grow well in dry climates, but since pomelos are relatively resistant to dryness, the first saplings were taken to a fruit research station in Kagoshima Prefecture. However, the volcanic-ash-covered Shirasu Plateau has weakly acidic soil, so the fruit was only mildly sweet. As a result, the southern region of Kumamoto was chosen for further cultivation in 1935.

Pomelo cultivation had already started in the Yatsushiro area, so it had receptive soil. Once again, the profitability of the banpeiyu attracted attention. Its flesh, easy to peel and eat, was another mark in its favor, and consumption steadily increased.

Selective breeding continued after the close of World War II ended Japan’s control of Taiwan. In 1960, banpeiyu production reached parity with native varieties, and since other regions produced relatively little, the fruit became known as a Yatsushiro specialtiy.

As a side note, the norm in Taiwan is to simply eat the flesh as it is, but in Japan there are many popular processed products focused on the bitterness of the peel, like candied peel and jam. And in Yatsushiro’s Hinagu Onsen hot spring, banpeiyu baths with the giant fruits floating in the water have become a winter tradition.

On January 27, 2023, this fruit also made headlines when a Yatsushiro banpeiyu officially made the Guinness World Records as “heaviest pomelo.” The fruit measured a massive 26 centimeters across and 28 centimeters high, and weighed in at 5,528 grams. Several of the previous records for the heaviest pomelo in the world had also been set by a Yatsushiro banpeiyu.

The record breaker was harvested in the Toyomachi district of Yatsushiro. In a fascinating coincidence, Shimada Yaichi was also born in Toyomachi. Shimada worked on a wide variety of other crops, but the one he spent most of his life on was the banpeiyu. And that banpeiyu, which he brought from Southeast Asia with his own hands, still grows in Taiwan and Yatsushiro and has become part of the local flavor.

It is an unknown story of the bonds between Taiwan and Japan.

A streetcorner fruit shop in Taiwan. Varied agricultural development went on during Japan’s colonial control, and many introduced species flourished. (© Katakura Yoshifumi)

(Originally published in Japanese. Banner photo: At fore, a banpeiyu from Yatsushiro in southern Kumamoto. Its size and weight are overwhelming. © Katakura Yoshifumi.)