Sweet Potatoes (Ipomoea batatas)
...and Yams (Discorea)

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Columbus himself was introduced to this member of the morning glory family by West Indians on Hispaniola during his second voyage--and promptly took them back to Spain, where they were quickly accepted there and across Europe. In fact, they were part of Catherine of Aragon's dowry, in her ill-fated marriage to England's Henry VIII; he may have rejected her (though she refused to acknowledge the divorce or leave England), but he was said to eat a couple dozen sweet potatoes at a sitting.

Following their conquest of Mexico, Spaniards then moved sweet potato plants to the Philippines. From there the Portuguese moved them to Malaya, Japan, China, and India. And we know that sweet potatoes made it to what became Virginia, in North America, by 1648, as they are described in Jamestown records from that time.

In China, they were established as a crop by 1594 and saw the nation through a number of droughts that blasted native grains. By the 18th century, it was written up in agricultural commentaries as a versatile crop that could be boiled, ground, and fermented; fed to animals and humans; grown in sand, on mountains, and in salty soils.

Why the rapid deployment when so many other New World foods were ignored? Easy: in a word, sex. They were reputed to be an aphrodisiac--as Dr. Muffet (supra) indicates.

That aside, sweet potatoes are a tropical vegetable--tubers that grow in the earth and send up lovely flowers that, yes, look like morning glories. And they not only can survive, but positively require fearful heat. Henry VIII tried to grow them, after he sent Catherine back to Spain, but couldn't--they withered on the vine in the cool English summers.

Because of their shape and growing region, they've acquired the "southern" nickname of "ocarina," a musical wind instrument invented in Italy in the late 19th century. [Interestingly, Italians called this instrument "ocarina" in the first place--meaning "goose egg"-- because of its shape and because it was made out of terra cotta. Such are the curiosities of language.]

"Gather the cotton in Mississippi or Alabama--dig and hoard the golden, the sweet potato of Georgia and the Carolinas,
Clip the wool of California or Pennsylvania,
Cut the flax in the Middle States, or hemp, or tobacco in the Borders,
Pick the pea and the bean, or pull apples from the trees, or bunches of grapes from the vines,
Or aught that ripens in all These States, or North or South,
Under the beaming sun, and under Thee."
--Walt Whitman in "A Carol of Harvest for 1867," Leaves of Grass (1900)

In the United States, sweet potatoes come in two basic varieties: a pale yellow, slightly sweet, dry variety that grows north; a dark orange, moist, distinctly sweet variety that grows deep south. In New Zealand, a purpley variety called Kumara grows that turns yellow green when peeled and cooked. West Indian sweet potatoes are enormous and very floury. Malaga pink sweet potatoes are made into a delicate tasting jam.

Although deep south sweet potatoes and yams look alike--and are commonly used interchangeably--they differ in both growth habit and culture. Yams belong to the genus Discorea. They are rarely grown outside of the tropics. They are less nutritious than sweet potatoes--are almost pure starch--and get slimy when they're cooked.