40 Fun Facts About Yams

Which Jamaican sprinter's father told reporters that Trelawny yams explained his son's speed?

Usain Bolt grew up in Trelawny, Jamaica's yam-growing heartland, a parish credited with at least half of the island's crop.

Hormones first made cheaply from wild Mexican yams paved the way for which medical breakthrough?

Oral contraceptives grew out of chemist Russell Marker's discovery that a compound in Mexican wild yams could be turned into cheap synthetic hormones, replacing costly animal extracts.

Which West African country grows roughly two-thirds of all the yams harvested worldwide?

Nigeria harvests about two-thirds of the global crop, and in its growing regions a farmer's social standing has long been judged by the size of his yam holdings.

Candied yams, a sweet potato dish of American Thanksgiving, are often topped with which confection?

Marshmallows crown a dish whose name is a misnomer: true yams grew rare in American kitchens, so the candied yams on the table are really sweet potatoes.

What is the Tagalog name for the purple yam that flavours Filipino ice cream and cakes?

Ube shares an ancient root with uwhi, the Maori word for the same yam, a trace of the seafarers who carried the plant across the Pacific.

At Abelam yam festivals in the Sepik region, a man traditionally gives his largest yam to whom?

His exchange rival is a permanent ceremonial partner who later hands over his own best yams, and the man who keeps giving the longer tubers gains great prestige.

In which country does the word yam usually mean oca, a small tuber first grown in the Andes?

New Zealand shoppers know oca simply as yams, though the plant is a wood sorrel from South America and no relation of the true yams.

In which US state has the air potato, a yam introduced in 1905, become a notorious invasive weed?

Florida struggles to clear the air potato because new plants sprout from its aerial bulbils, and the stems grow back from buried tubers even after being cut down or burned.

Which US state promoted its sweet potatoes as yams with a Yambilee festival in Opelousas?

Louisiana held its first Yambilee in 1946 to win nationwide publicity for the state's sweet potatoes, and the festival ran until 2012.

A South African yam with a huge corky stem above ground is named after which animal's foot?

Elephant's foot yam earns its name from a domed stem armoured with thick, hard plates, which can grow to more than three metres around.

Which Chinua Achebe novel follows Okonkwo, a West African yam farmer, as colonisation arrives?

Things Fall Apart began as a much longer draft: Achebe cut its second and third sections, kept only the yam farmer's story and published it in 1958.

Iyan, or pounded yam, is traditionally made in West Africa by beating boiled yam with which tool?

Mortar and pestle work turns boiled yam into a dough similar to mashed potatoes but heavier, which is served with rich soups and stews.

In Malaysia and Singapore, yam usually means which other root, the one mashed into Hawaiian poi?

Taro belongs to the arum family, not the yam family, yet it borrows the yam name in both countries.

Which crunchy Mexican root, usually eaten raw with lime and chili, is also known as the yam bean?

Jicama is no yam at all: the vine belongs to the pea family and bears pods much like peas above its crisp, sweet root.

Which Filipino shaved-ice dessert is often topped with purple yam jam?

Halo-halo is often translated as mix-mix: sweet beans, fruit and jellies sit under shaved ice and milk, topped with purple yam jam, flan or ice cream.

Which US agency requires any food label that says yam to also carry the words sweet potato?

The USDA rule exists because the orange yams in American shops are soft sweet potatoes, a nickname first given by enslaved Africans who saw a likeness to the yams of home.

West African yam farmers often prefer digging tools of which material, as it damages fewer tubers?

Wood is gentler on the fragile tubers than metal, though such tools wear out fast; a damaged yam stores badly and soon spoils.

The word yam is thought to come from West African words such as Fulani nyami, meaning what?

To eat is the sense of Fulani nyami; English picked the name up in the 1580s by way of Portuguese inhame or Spanish igname.

The Chinese yam is nicknamed after which spice because its small flowers carry the same scent?

Cinnamon vine is the plant's other English name, and it is the rare yam whose tubers are safe uncooked, grated into a slippery paste.

Which West African people celebrate Iri Ji, the festival that must precede any tasting of new yams?

Igbo communities first offer the new yams to gods and ancestors, and in some places every old yam must be finished or thrown out on the eve of the feast.

The orange yams in American supermarkets are really sweet potatoes, members of which plant family?

Morning glory vines and sweet potatoes share the family Convolvulaceae, while true yams sit in a family of their own, so the two crops are not related.

Jinenjo, a wild mountain yam, is a traditional binder in the dough of which Japanese noodle?

Soba makers prize jinenjo for its unusually strong, stable stickiness; the same native yam is often foraged from the wild.

Grated nagaimo yam is a classic ingredient in the batter of which savoury Japanese cabbage pancake?

Okonomiyaki batter mixes flour, eggs and shredded cabbage with grated nagaimo, a long yam that acts as a binding agent.

Raw yam contains more of which mineral than any other of the world's ten major staple foods?

Potassium is where yam outranks every other major staple, yet the tuber is a poor source of protein, at around 2 percent of its fresh weight.

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

Lilies and grasses share with yams a single seed leaf, the mark of a monocot, whereas sweet potatoes sprout with two.

Which water-soluble pigments give purple yams the violet colour that tints ice cream and cakes?

Anthocyanins colour purple yams so strongly, and dissolve so readily in water, that they have been proposed as natural food dyes.

Pounded yam belongs to a group of West African dough staples known by which name?

Swallow foods get their name from the way they are eaten: a piece is pinched off, rolled into a ball, dipped in soup and gulped down without chewing.

Yams' genus Dioscorea honours Dioscorides, a Greek physician whose five-volume work covered what?

Herbal medicine was the subject of his De materia medica, which was read for more than 1,500 years and stayed at the core of European pharmacy into the 19th century.

In which Pacific country do Trobriand Islanders treat yams as currency and stack them in yam houses?

Papua New Guinea's Trobrianders count yams as wealth: each year a man grows them for his sister, and the more she receives, the richer and more powerful she is.

US biologists have released which insects to chew through the invasive air potato yam?

Beetles of the species Lilioceris cheni feed on the air potato and, like the yam itself, come from Asia, which made them a natural choice for biological control.

Which sticky Japanese side dish is made by grating raw mountain yam and is often poured over rice?

Tororo takes its name from torotoro, a Japanese sound-word for anything sticky or syrupy, and the yam is peeled first because its skin can make hands itch.

Which translucent Japanese noodles, often sold as yam noodles, actually come from the konjac plant?

Shirataki means white waterfall, and the konjac corm behind the noodles belongs to the arum family, so the yam in the name is only a nickname.

In Indonesia, an extract of the air potato yam has traditionally been used to prepare what?

Arrow poison can be made from the air potato because its bitter forms are toxic; cooks who use them must first soak, ferment or roast the grated tuber.

Mexican villagers who dug wild yams for hormone makers were often told the roots would become what?

Soap was the cover story given to the barbasqueros, the diggers who pulled the tubers from the jungle with sticks or bare hands, often without learning the real use.

Before making hormones from Mexican yams, chemist Russell Marker devised which famous measurement?

Octane rating was Marker's idea while he worked at the Ethyl Corporation, years before he founded a steroid industry in Mexico built on wild yams.

Chemists can turn diosgenin from wild yams into which hormone, a step the human body cannot perform?

Progesterone can be built from yam diosgenin only in a laboratory, so wild yam creams and supplements have no such hormonal effect inside the body.

Which poisonous European hedgerow climber with bright red berries belongs to the yam family?

Black bryony is poisonous from berries to tuber, though its young shoots are picked and cooked as a vegetable while still low in toxins.

Botanists tell the winged yam from the air potato by which feature of their climbing stems?

Twining direction separates the two: the winged yam always spirals clockwise up its support, while the air potato winds the opposite way.

Purple yam is mostly sterile, so its spread from Madagascar to Polynesia traces which seafarers?

Austronesians carried the yam in their canoes as a staple, and because most varieties cannot seed themselves, wherever it grows marks a human landing.

Which dark brown Yoruba dish is made by stirring flour from sun-dried yam into boiling water?

Amala owes its colour to the drying: yam flesh is white when fresh but turns brown in the sun, and the milled powder is known as elubo.