A Strange Fruit

Visiting a Water Caltrop Farm in Tainan

Text: Rich Matheson
Photos: Rich Matheson

The water caltrop (Trapa bicornis) is an aquatic plant with a fruit strangely shaped like Dali's moustache – although it is more often likened to the shape of a bull's horns. The fruit is alternately called ling nut, horn nut, bat nut, devil pod, and, in Chinese, ling jiao. On a recent trip to southern Taiwan, Travel in Taiwan found out more about this exotic fruit, the seed of which is edible.


Native to parts of Eurasia and China, there is evidence that the water caltrop has been cultivated for three thousand years. The genus Trapa was once found in North America, but disappeared prior to the Pleistocene. The fruit, rarely found in the West, becomes a ubiquitous part of southern Taiwan's landscape from September through December, when stands sporting signs with its distinct taurine shape line the roads. Throughout Tainan's Guantian District, during water-caltrop season you can see farmers in hip waders harvesting the fruit. Others will be squatting in small canoes to harvest fields too deep to wade through. This traditional method was originally employed when water caltrop was grown in deeper waterways and natural wetlands rather than in dedicated paddies.

You can see farmers in hip waders harvesting the fruit; others will be squatting in small canoes to harvest fields too deep to wade through

Li Wen-yu, of the Guantian District Farmers' Association, explains to us that the ling nut was introduced to Taiwan during the time when Ming Dynasty loyalist and military leader Koxinga (1624~1662) had his headquarters in the Tainan area. At that time, Guantian was dotted with muddy pools created after the excavation of clay used in the area's brick kilns. The area offered easy access to water, and the clay soil was ideal for water caltrop. Guantian long enjoyed a virtual monopoly in Taiwan’s water-caltrop market, until about a decade ago when farmers in other areas, mainly Kaohsiung and Pingtung counties, began cultivating water caltrop as well. There followed a few difficult years for Guantian farmers as market prices fell, but the situation has improved in the last several years, spurred in part by the introduction of organic cultivation. Yang Cong-gui, chief of operations for the Friendly Earth Organic Alliance, a cooperative of farmers who share the dream of turning Taiwan into an organic paradise, kindly agreed to show Travel in Taiwan around his Guantian-based operation. When Yang was only 18 he decided he wanted to be an organic farmer, but he had to wait until he was 37 and after he had ended a career in technology before embarking on his dream. He established a lab/classroom consisting of six pools for research. Following two years of studying the local eco-system and critically weighing matters of ecology and habitat, Friendly Earth was founded in 2010. Yang says the public must be educated not only on the cost to human health from the harmful chemicals used in agriculture, but also on the environmental costs caused by regular farming. Guantian has 350 hectares of water-caltrop paddies, of which about 3-4% are cultivated organically, without the use of chemicals. In 2011, Friendly Earth had seven organic farmers and 3 hectares of organic fields. The following year there were 15 organic farmers, harvesting 8 hectares. Today, 30 work 17 hectares. Mr. Yang stresses that the most important quality his organic farmers possess is their “heart.” According to him, only about 5% of Taiwan’s farmers meet government standards on the safe use of chemicals, the non-use of chemicals, or organic farming. With both regulations and law enforcement leaving much to be desired, he says, when it comes to organic farming the most important factor is the farmers’ personal desire and commitment to creating the best product they are capable of while being as careful with area ecology as their knowledge enables. Among its various initiatives, Friendly Earth championed successful efforts to protect the pheasant-tailed jacana. Guantian's caltrop paddies are the main breeding grounds for these waders, and the use of chemicals in agriculture was causing the population of this rare and valuable bird to dwindle. Today there is a healthy population.

From the first to fourth months each year, caltrop seedlings are grown in successively larger tubs of water, and around the Dragon Boat Festival, which is generally in June, the plants are transplanted to the water-filled paddies. Three months later the harvest begins, usually starting in time for the Mid-Autumn Festival around September, and lasting through to December. In the final month of the year, rice is planted, and after the rice harvest in the next year, the field is baked in the sun to prepare for the next water-caltrop planting. Crops are rotated, and each field is left fallow for a year every 2-3 years. After our chat with Mr. Yang, we carry on to a caltrop field where a busload of schoolchildren is learning about their renowned local crop. Local farmer Xu Yu-can is explaining harvest techniques to the children, and later gives them a chance to wade in the field and harvest the horny nuts. During the harvest months, the farmers rotate through their fields, picking each clean in turn, eventually arriving back at the field where they started. Then they start circling again. These cycles continue until the end of the harvest – signaled by the coming of the north wind, usually in mid-December. Farmer Xu says that an ideal water-caltrop plant produces 32 harvests in its lifetime, and the highest-quality water caltrops are harvested in October – they have the finest taste. Li Wen-yu of the Guantian District Farmers' Association explains the association’s role in the water-caltrop harvest to Travel in Taiwan. “We first collect water caltrop fruit from the individual farmers, and the fruit is thoroughly cleaned in a large vat of water. All fruit that floats to the top is optimal for immediate consumption; these are shelled and sent to vendors or restaurants. The remaining select fruit are hand-sorted according to size, and the horns are inspected to see if the thin skin layer that covers the hard shell is damaged. Rotten fruit are disposed of. The remaining fruit are either shipped to farmers’ markets in 20kg bags or immediately frozen to retain freshness.” The larger fruits aren't necessarily tastier; they just look better. In fact, explains Mr. Li, you can't tell if a fruit is tasty and fresh until you have shelled it. The smell is telling, however. A fragrant ling nut will taste good, a pungent one will not, and one with no smell will be tasteless.

The smell is telling. A fragrant ling nut will taste good, a pungent one will not, and one with no smell will be tasteless

Water caltrops are typically prepared for consumption with a 40-minute boil. The shells are very hard and sharp, so caltrops are often sold already shelled, for which a special knife is used. A great snack, they are filling and are said to be good for hangovers and fever.

In the afternoon we visit Kai Hsuan Restaurant, where proprietor Yang Mei-e has prepared the restaurant’s popular water-caltrop set meal (book a day in advance, as the dishes take time to cook and prepare). She states that the restaurant is well known simply because it is the only restaurant specializing in water caltrop. That said, the food is superb. The pork caltrop soup is seasoned with cilantro and the subtle taste of the fruit is effused with the pork's flavor. In season, the water caltrop are fresh, direct from the farms, but with a three-day shelf life, frozen fruit are often used and can be kept for a year without losing freshness. Mrs. Yang says they use fruit that is not too ripe nor too young, just right, otherwise the meat would be too watery or tough respectively. The most flavorful dish we sample is deep-fried caltrop coated in a bread crumb mixture, which is crunchy, starchy, and filling. Finally we try sesame oil water caltrop with sticky rice. The caltrop in this dish brought to mind a russet potato texture; a stickier starchier version of the fruit. Next time you see this strange horny fruit being sold on the roadside in southern Taiwan, don't pass up the opportunity – buy a bag to munch on as you drive on.


English and Chinese

Friendly Earth Organic Alliance友善大地有機聯盟
Guantian District官田區
Li Wen-yu李文裕
ling jiao菱角
Xu Yu-can許玉燦
Yang Cong-gui楊從貴
Yang Mei-e楊美娥


Kai Hsuan Restaurant (凱旋餐廳)
Add: 41-1, Sanjieyi, Guantian District, Tainan City (台南市官田區三結義41之1號)
Tel: (06) 579-4020



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