Adzuki beans, which are known in Chinese as “red beans” or “little beans,” are annual plants native to the Himalayan Mountains. Mainland China, Japan, Taiwan and Korea comprise the main places the beans are cultivated. Smaller amounts are grown in India, Southeast Asia, Canada, and the United States.

Since Taiwan joined the WTO in 2002, it has maintained tariff rate quotas on adzuki beans and banned all imports of them from mainland China. Total imports of the beans have averaged about 4,000 metric tons per year.

It is not entirely certain how these red beans from the Himalayas made it to Taiwan. It’s generally thought that adzuki beans were first planted only in high-elevation areas here. It wasn’t until the beans were planted as a fall crop in Pingtung in 1960 that they became an important cash crop.

The classic flavor of adzuki bean pastries (above), as well as the mouthfeel of adzuki popsicles with their crunchy outsides and succulent insides (left), are etched deeply into the childhood memories of Taiwanese.

Generally speaking, rice isn’t planted in the fall and winter in Taiwan. That’s the time instead for various non-rice staple crops, including adzuki beans. From the end of September to the middle of October, farmers sow the adzuki seeds after harvesting the second crop of rice from their paddy fields. Then they harvest the beans three months later.

Chen Yu-ju, a researcher with the Council of Agriculture’s Kaohsiung District Agricultural Research and Extension Station, explains that adzuki requires weather that’s “first hot and then cold.” Especially when the pods begin to fatten, if the weather is too hot, the pods will be smaller. In other words, the most suitable time to plant adzuki is in the early fall before the warmth of summer has entirely dissipated. Then the weather can gradually cool to the chill of winter.

According to COA statistics, adzuki beans are the nation’s fourth most important “non-rice staple.” Currently, 5,600 hectares of adzuki are under cultivation each year, behind only peanuts, corn (maize) and sweet potato. Its total value is estimated at NT$530 million.

Surprisingly, though most Taiwanese think of green mung beans and adzuki beans as comparable products, the area of adzuki under cultivation in 2011 was 112 times as large as that for green mung beans (5600 to 50 hectares) and the quantity harvested was 267 times as large (11,498 to 43 metric tons). Among beans, adzuki are in a league of their own.

Pingtung County is the center of Taiwan’s adzuki bean farming, accounting for more than nine-tenths of total production. Located near the border of Kaohsiung and Pingtung, the COA’s Kaohsiung District Agricultural Research and Extension Station is responsible for improving adzuki strains. In July of this year, it released a new variety: Kaohsiung No. 10 (“Red Jade”). It is now entering the phase of technology transfer and commercialization. The strain may be cultivated commercially as early as next fall.

Kaohsiung No. 9 (“Red Treasure”) is currently the variety of adzuki most favored by farmers and consumers in Taiwan. It accounts for about 60% of the area under cultivation.

Chen Yu-ju loves her job of breeding new adzuki varieties, though the work is by no means fast or easy.

This is how Chen Yu-ju, the researcher behind the development of both “Red Treasure” and “Red Jade,” sums up the ultimate goal of adzuki breeding: “To attain a prettier color and a fatter bean.”

Chen says that bright red is adzuki’s ideal color. In terms of weight, if 100 beans weigh 14 grams or less, then the variety is regarded as small; at 14.1–17 grams it is regarded as medium sized; at 17.1–20 it’s large; and at 20.1 and over it’s extra-large.

“From the start of breeding to release, the process of developing a new variety takes 10 years,” explains Chen. “The breeding has always taken so long because each year you only get one chance to plant in the fields—in the fall,” she explains. “What’s more, you’ve first got to do thorough research into a bean’s ancestors. You can’t overlook any detail of its genetic heritage, since the more you know about the ancestors, the more you can control the characteristics of the descendants.”

So what improvements have been made to adzuki bean varieties in Taiwan so far?

When one examines the evolution of adzuki beans in Taiwan, Kaoshiung No. 1, which was introduced in 1974, is the place to start. Its descendants include Kaohsiung Nos. 2, 3 and 5­­–10. Each is larger and brighter red than its predecessors.

It was just 38 years ago, in 1974, that the COA’s Kaohsiung District Agricultural Research and Extension Station introduced Kaohsiung No. 1. The variety was bright red, but had a significant flaw: It was small, with 100 of its beans weighing less than 14 grams.

What’s more, Kaohsiung No. 1 was highly susceptible to powdery mildew fungal disease. When afflicted, the leaves of adzuki plants become covered with a powdery white film that impedes photosynthesis, leading to stunted growth and lower yields.

Early in 1980 the Kaohsiung Station released Nos. 2 and 3 in rapid succession. But like No. 1, they had the flaws of being small and offering only low yields.

Kaohsiung No. 5, released in 1988, was the first variety that Chen worked on. It was crossbred from a Pingtung variety and Kaohsiung No. 1. It combines the steady yields of the former with the bright red coloration of the latter. The plants tend to grow taller and straighter than earlier varieties, and they aren’t easily toppled over. In comparison to earlier varieties, Kaoshiung No. 5 offers increased yields of 10–15%. The beans also have thinner skins. Their mouthfeel, moreover, is more refined, and they feature a stronger fragrance.

Pods of smooth red beans grow concealed in lush green adzuki fields.

In order to advance the quality of Taiwan’s adzuki beans, it has been necessary to import varieties from abroad to use for crossbreeding. After Kaohsiung No. 5 was released, Chen and her colleagues began to crossbreed it with a variety from Hokkaido, Japan. Although the Japanese variety offered high yields and its large beans were regarded as superior to Kaohsiung No. 5, it had its own drawbacks: a dark coloration and shorter plants.

After selection and purification over the following generations, Kaohsiung No. 6 was released in 1993. It offers plants of extremely uniform size. Moreover, it inherited the bright red of its mother, Kaohsiung No. 5.

Chen believes that for breeding purposes all strains have their good points and bad points, including KS540, a rejected variety that shares parents with Kaohsiung No. 5.

KS540’s dark coloration is not appealing to people, but the plants are larger than Kaohsiung No. 5. Taking that unappreciated variety as the mother and “Mikandainagon,” a Japanese variety, as the father, Chen was able to develop a new strain: Kaohsiung No. 7, the first of the large-seeded varieties released by the research station, which was launched in 1998.

Apart from working hard to improve strains, the research station has also spent a lot of energy fighting damage from disease and pests. In particular, powdery mildew and chilli thrips commonly inflict devastation in adzuki fields.

Since 1990 the Kaohsiung research station has thrown itself into disease-prevention work. By crossbreeding KA79-02-07, a variety it developed itself, with the Japanese Mikandainagon, it was able release Kaohsiung No. 8 in 2002. This variety greatly reduces the problem of field pests and the costs associated with disease and pest control. Nevertheless, its smaller beans (ranked as medium size) represent a big flaw.

Consequently, the Kaohsiung research station subsequently focused on improving the size of Kaohsiung No. 8 beans and released Kaohsiung No. 9 (“Red Treasure”) in 2006. Its beans weigh in at 23 grams per 100, making it the largest of the station’s adzuki varieties to date. Since its release, domestic and foreign farmers alike have been continually inquiring about the possibility of obtaining seeds.

In July of this year the research station issued its newest varietal release: Kaohsiung No. 10 (“Red Jade”). With its coloration, overall appearance, and sales appeal, it’s the best variety developed in Taiwan so far.

The classic flavor of adzuki bean pastries (above), as well as the mouthfeel of adzuki popsicles with their crunchy outsides and succulent insides (left), are etched deeply into the childhood memories of Taiwanese.

According to the COA, in Taiwan there is annual demand for 12,000 metric tons of adzuki beans and related processed goods. About 8000 tons of that is met from local production.

Pingtung County’s Wandan grows the most adzuki beans in Taiwan. The township’s farmers’ association explains that barring unusual rain damage, its 13 production cooperatives will harvest more than 4000 metric tons each season. About four-tenths of that is put on the commodity market, and about six-tenths is sold directly to processed food manufacturers to make adzuki bean paste and other processed foods.

The domestic market takes almost all of local adzuki bean production, and very little is exported. Although it’s hard for Taiwan-produced adzuki beans to compete on the international market with low-priced beans from mainland China, the international reputation of Taiwan adzuki beans is steadily rising. UTC Foods, which is working closely with adzuki producers in Pingtung, has attained orders from the United States, Canada and elsewhere, as well as from the international coffee chain Starbucks, which is supplying its locations in the Asia-Pacific region with beverages made from adzuki beans and green-tea powder.

The district of Daliao in Kaohsiung broke new ground last year by releasing unprocessed adzuki beans, marketed under the name “Red Diamond.” These well-received beans have attained Traceable Agricultural Product certification from the COA. Daliao’s farmers’ association says that it can sell at least 10 tons a year on the domestic market and that it is in discussions to export to Brunei.

Why are the locally produced beans better than the imported stuff?

Chen explains that the locally grown adzuki beans are larger than the imported varieties, and their smooth mouthfeel and fine consistency are also clearly superior to the harder and grittier imported beans. What’s more, the locally produced beans have a naturally sweet flavor without the need for a sweetener.

To sample the sweet taste of joy, you needn’t go far: Taiwan-grown adzuki beans are right at hand.

Pods of smooth red beans grow concealed in lush green adzuki fields.

One mouthful of this steaming hot adzuki bean soup with its joyous flavors and simple fragrance and you’ll feel warmed to the bottom of your heart.