Colourful Traveller

The sweet potato crossed the Pacific long before Columbus did, and is celebrated throughout the tropics.

Next time someone asks you to go and pick up some potatoes, don’t think of complaining that it’s too far to the shops, or you just don’t have time. Instead just think of the ancient Polynesians. Why? Their shopping trip is worthy of the Guinness Book of Records; for them, nipping to the market was not to be lightly undertaken. Here’s how they got their potatoes, or in this case, sweet potatoes.

Firstly they constructed inordinately seaworthy boats, big double-hulled catamarans that needed to be impossible to capsize. This was because they had to cross the Pacific and get to South America. Even though they were skilled traders and explorers, they had little idea where they were going, or if they would ever get there – or even get back. It was a seriously long-haul trip: some 5,000 miles of inhospitable ocean. Their enormously long journey was filled with maritime perils, but they completed their voyage and lived to tell the tale – at least to their families – as well as bringing back sweet potatoes. The vegetable took off in Polynesia and it became part of the regional diet – no more long journeys needed to be made.

Centuries were to pass before Captain James Cook anchored in Polynesia, in 1769, and picked up some of the sweet potatoes and brought them back home to Britain. They’ve been carbon-dated since and have had their genetic blueprint established. The potatoes can be traced back to Ecuador and Peru. In fact, all sweet potatoes can be; this is where they originated.

Meanwhile, archaeologists have carbon-dated prehistoric remains of sweet potato found in Polynesia itself, and have established that crops were growing on the islands as early as 1000 or 1100 AD. The two findings seem to show that sweet potatoes were introduced from South America to Polynesia an astonishing one thousand years ago. Further clues bear this out: one of the Polynesian words for sweet potato is ‘kumala’, which is hardly a stone’s throw away linguistically from ‘kumara’, the Quechua name for the vegetable.

This suggests that the Polynesians and South Americans were trading with each other long, long ago – certainly hundreds of years before Columbus officially discovered America. The sweet potato was also introduced by the Polynesians to Asia, and then finally re-introduced by the Spanish and Portuguese as they crossed the globe from South America. The vegetable’s certainly well-travelled and you can now find it far from its original source. Sweet potatoes are cultivated throughout tropical and warm temperate regions wherever there is sufficient water to support their growth. You can even find them growing in parts of Europe, notably Portugal.

Sweet potatoes spread from Polynesia to China and Japan. In China, following a crop failure in 1594, they were introduced to the province of Fujian. And then around 1735, the shogun Tokugawa Yoshimune welcomed them into his garden in Japan and grew them there – they eventually became a Japanese staple. They were soon introduced to Korea, where they also flourished. Not only are they delicious but they're dependable. Where to turn when your crops have been devastated by a typhoon? The sweet potato is the answer, and its hardiness explains why it’s so extensively found in the tropics. Indonesia, Vietnam, India, and other Asian countries are also large sweet potato growers.

The sweet potato is a bright orange vegetable, and unlike the potato, it’s not a tuber, but a root crop. The root swells and it’s the swelling that’s harvested, cooked and eaten. It’s prepared in a similar way to butternut squash, parsnips, swede and turnips.

The sweet potato, unlike the usual white potato, counts towards your 5-a-day because they are low in starch. They're also incredibly good for you. They’re a source of four crucial nutrients: vitamin C, thiamine, potassium and manganese, which collectively have many health benefits. A large sweet potato contains more than 70% of our daily recommended intake of vitamin C. When it comes to bone health, manganese is very important, and it also protects us from the damage caused by stress. Thiamine is one of the B-vitamins that promote the wellbeing of our nervous system and also our hearts. Potassium regulates the contraction of our muscles and helps our blood pressure to stay within normal limits.

Nutrition aside, the great advantage of sweet potatoes is their sheer easiness to prepare: you can mash them, roast them, boil them, sauté them, add them to a massaman curry – just about anything you can do with usual potatoes. You can even make fries with them. On Samui you'll find them at every market and you'll have no difficulty in recognizing the mounds of swollen roots on display. They go particularly well with any curry that uses coconut milk and especially chicken. They're also found in many recipes involving peanuts.

Throughout the tropics, recipes involving sweet potatoes are legion and very different from each other. Sun-dried and crushed roots make for a staple breakfast for Ugandans and are eaten with peanut sauce, while the root, baked in earth, provides a snack to be eaten throughout the day. Sweet potato leaves meanwhile are eaten in West Africa, as they are very healthy. In Egypt sweet potato is sold from special carts with in-built ovens, and are also home-baked for desserts that are then lavishly topped with honey.

In parts of India, sweet potato is popular during fasts due to its health properties. A common way to prepare them is to slow-roast the roots over kitchen coals and then eat with yoghurt. Elsewhere in India dried sweet potato is turned into flour which is then mixed with wheat flour to produce chapattis.

In Japan, where the sweet potato is known as ‘satsuma-imo’, it’s simply boiled or steamed and then eaten. The Japanese also bake it into a sweet dessert. Perhaps the most unusual use is to make shochu, a Japanese spirit normally made from the fermentation of rice but which can also be made from sweet potato. In the 1990’s Japan’s most long-lived citizen, at 104 years old, ascribed part of the reason for his abundant longevity to the spirit. (His doctors meanwhile disagreed and were begging him to at least cut down on his alarming daily consumption.)

The sweet potato may make for a potent and even lethal spirit, but it’s more associated as a life-giver; its crops save many lives when other vegetables may fail. And those who eat sweet potatoes are doing their bodies a massive favour. It’s certain that the root was always destined to prove popular with farmers, governments and chefs, but it seems that those early Polynesian pioneers were the first people to bring them home and grow them.