40 Fun Facts About Sweet Potatoes and Yams

A compound made from wild Mexican yams by chemist Russell Marker paved the way for which landmark medicine?

The contraceptive pill grew out of the cheap progesterone Marker learned to make from yam roots, founding a steroid industry in Mexico. He had earlier invented the octane rating for fuel.

Cultivated sweet potatoes are a natural GMO, carrying genes picked up long ago from which kind of organism?

Bacteria of the Agrobacterium group inserted their DNA into an ancestor of the crop, and the genes still work today. That makes sweet potato the first known naturally transgenic food crop.

Sweet potatoes are only distant cousins of ordinary potatoes and belong to which flowering plant family?

Morning glory is the family, and sweet potato is its only major food crop. The ordinary potato sits with tomatoes among the nightshades, and true yams are more distant still.

Candied yams, the sweet potato side dish of American Thanksgiving, are often baked under which topping?

Marshmallows melt over a dish that contains no yams at all. The name is a misnomer, because true yams became rare in American kitchens after colonial times.

Which West African country grows about two-thirds of all the true yams harvested in the world?

Nigeria harvested 67% of the world's yams in 2020. The crop is so prized in the region that many communities hold a festival before anyone may eat the new harvest.

The word yam reached English through Portuguese or Spanish from West African words with which everyday meaning?

To eat is the root sense, from words such as the Wolof for food. Enslaved Africans in America are said to have given the name to the sweet potatoes that reminded them of home.

Long before Europeans reached the Americas, sweet potatoes were already grown across which Pacific region?

Polynesia had the crop at least 600 years ago, as dated remains in the Cook Islands show. The leading idea is that island voyagers reached South America and sailed home with cuttings.

The vivid purple yam behind Filipino jams, cakes and ice cream is best known by which Tagalog name?

Ube is a true yam, and nearly all its varieties are sterile, so it reached each Pacific island only in human hands. That makes it a living tracer of ancient voyages.

Sweet potatoes once supplied most of the calories in the traditional diet of which Japanese islands?

Okinawa got about 69% of its calories from sweet potatoes around 1950, with rice a distant second. The crop had arrived in the early 1600s, when the islands were the Ryukyu Kingdom.

In New Zealand, sweet potatoes are sold under which name, taken from the Māori language?

Kūmara came with the first Māori settlers, who grew finger-sized yellow varieties. Larger kinds brought by American whalers in the early 1800s soon took over.

The English word potato descends from batata, the sweet potato's name in which indigenous American language?

Taíno speakers of the Caribbean gave the Spanish the word batata. Spaniards are thought to have blended it with papa, an Andean word for the ordinary potato, to make patata.

George Washington Carver wrote farm bulletins on sweet potatoes and peanuts while teaching at which institute?

Tuskegee was where Carver logged scores of sweet potato products, among them 73 dyes, 14 candies and 5 library pastes. He urged poor farmers to grow the crop to feed themselves.

Which state, the top sweet potato grower in the United States, made it the official state vegetable in 1995?

North Carolina has ranked first among sweet potato states since 1971. Fourth-graders in the town of Wilson petitioned lawmakers for the honour after a visit from their local representative.

Sweet potato pie, a holiday dessert of the American South, stands in for a pie filled with what?

Pumpkin is the holiday pie elsewhere in the country. Enslaved Africans likely used sweet potato as a stand-in for the yam of their homeland, and European pie-making did the rest.

The first Europeans to taste sweet potatoes, on Hispaniola, belonged to an expedition led by which explorer?

Christopher Columbus's expedition met the crop in 1492, and it crossed the Atlantic soon after. By 1604 it was turning up in an English country-house recipe book.

Ceviche is traditionally served with boiled sweet potato, called camote, in which South American country?

Peru pairs its citrus-marinated fish with sweet potato and has prized the root for millennia. Potters of the ancient Moche culture there shaped vessels like sweet potatoes.

Which Japanese spirit, usually made from rice or barley, is also famously distilled from sweet potatoes?

Shōchū distilled just once keeps the strong taste and aroma of its sweet potatoes. A boom in the drink in the early 2000s caused a serious shortage of the roots in Japan.

Dangmyeon, the chewy glass noodles made from sweet potato starch, are the heart of which stir-fried dish?

Japchae began as a noodle-free vegetable dish that so pleased a 17th-century king he promoted its inventor to high office. The sweet potato noodles joined only in the 20th century.

Sweet potatoes are usually grown not from seed but from sprouts taken off a stored root, known as what?

Slips are shoots that sprout from a root kept in storage, each one planted out to become a new vine. True seeds are used only by breeders.

Orange-fleshed sweet potatoes are promoted across Africa to fight a widespread deficiency of which nutrient?

Vitamin A is made in the body from the beta-carotene that colours the flesh. Breeding and spreading these roots earned their champions the World Food Prize in 2016.

True yams are monocots, which makes them closer relatives of which plants than of sweet potatoes?

Lilies and grasses are monocots, sprouting with a single seed leaf, and yams belong with them. Sweet potatoes are dicots, so the two look-alike crops sit on far-apart branches of plant life.

At the market, a true yam can be told from a sweet potato by which kind of skin?

Rough and hard to peel is the giveaway, though cooking softens it. Inside, the flesh runs from white or yellow to purple or pink, and a tuber can reach 1.5 metres down into the soil.

Most yams must be cooked to be safe, but Japan's nagaimo yam is commonly served in which way?

Raw and grated nagaimo becomes tororo, a sticky purée poured over rice, noodles or tuna. Cooks soak the tuber in vinegar water first so its needle-like crystals do not irritate the skin.

The air potato, a yam vine introduced in 1905, has since become an invasive pest across much of which US state?

Florida cannot shake it, because new vines sprout from the potato-sized bulbils that grow along the vine, even after cutting or burning. Wild forms growing there can be poisonous.

The New Yam Festival, called Iri ji or Iwa ji, is the great harvest celebration of which West African people?

Igbo custom holds that nobody touches the fresh crop until the feast, when yams are first offered to gods and ancestors. One scholar called them the most enthusiastic yam growers in the world.

In Malaysia and Singapore, the word yam on a menu usually means which other starchy crop?

Taro takes the name there, one of several unrelated plants called yams. Others include the yam daisy of Australia and the elephant foot yam of Asia.

In New Zealand, the small pink tubers sold as yams are actually which Andean crop, a kind of wood sorrel?

Oca became a popular table vegetable in New Zealand after arriving in the 19th century. It is no relation of the true yams, which sit in a separate plant family.

The botanical genus of the true yams was named in honour of which ancient Greek physician and botanist?

Dioscorides gave his name to the genus Dioscorea, chosen by the monk and plant collector Charles Plumier. It holds hundreds of species, a few grown for food and others toxic.

Dried yam ground into flour and stirred into boiling water makes which dark Yoruba dish, eaten with soups?

Amala turns dark brown because the yam slices darken as they dry in the sun before milling. The flour itself is called elubo.

On which islands of Papua New Guinea are yams valued as a currency that stands for wealth and power?

In the Trobriands, custom has a man give his yam harvest to his sister's household, so that her children are fed by their mother's line rather than their father's.

Sweet potato casserole, a mashed Thanksgiving side dish, is typically topped with brown sugar and which nut?

Pecans suit a dish from the American South, where sweet potatoes have long been a staple. Americans got through about 13 kg of them each in 1920, a figure that later fell to around 2 kg a year.

Which country grows far more sweet potatoes than any other, harvesting about half of the world's crop?

China harvested 55% of the global crop in 2020. The plant arrived there around 1594 from Luzon after a major crop failure, and a provincial governor urged farmers to grow it.

Māori traditionally cook sweet potatoes in a hāngī, which is what kind of cooking setup?

An earth oven cooks food buried underground, and the hāngī is still fired up when large gatherings meet on a marae.

A sweet potato is a swollen storage root, whereas an ordinary potato is a swollen underground what?

Stem tissue swelling at the tips of underground runners forms a potato. A sweet potato is a true root, one more sign that the two crops are only distant relatives.

Purple sweet potatoes owe their colour to which family of pigments, also found in blueberries and red cabbage?

Anthocyanins can look red, purple or blue depending on acidity, and an extract of purple sweet potato is used as a natural food colouring.

Beauregard, the orange sweet potato that dominates Australian farms, was bred in which US state?

Louisiana bred Beauregard in 1981, and it now makes up about 90% of Australia's crop. French and Spanish settlers took to sweet potatoes early, giving the state a long growing tradition.

Which leafy Asian vegetable, also called kangkong, is a close relative of the sweet potato in the genus Ipomoea?

Water spinach is one of the few other food plants in a family of more than 1,000 species, many of them poisonous. It is grown in wet tropical ground for its tender shoots.

Camote cue, a Filipino street snack of sweet potato fried in caramelised brown sugar, is sold in which form?

On bamboo skewers is how it is handed over, though the slices are fried loose and threaded afterwards. It is among the most common street foods in the Philippines.

After harvest, sweet potatoes are held warm and humid for days so skin wounds heal, in a step called what?

Curing also improves flavour, and the roots can then keep for about 13 months in cool, humid storage. Colder temperatures injure them.

In which country do pizza chains such as Domino's and Pizza Hut offer sweet potato as a popular topping?

South Korea calls the root goguma and also roasts it in drum cans as winter street food, sold by vendors in fur hats with ear flaps.