FEW VEGETABLES HAVE had to suffer the ignominies faced by the venerable sweet potato. Mislabeled, misnamed and inextricably bound to the thick white goo of melted marshmallows, molasses, brown sugar or maple syrup, the sweet potato nonetheless has managed to find a respectable spot in cuisines around the world. Some varieties are successfully grown here in the Hudson Valley, and its versatility in a wide range of dishes (with or without marshmallows) should put the bright orange tuber on more shopping lists, and not just around Thanksgiving.
The sweet potato is indigenous to Central and South America; archeological evidence found in Peruvian caves proves that it’s one of mankind’s oldest cultured vegetables. The recent discovery of prehistoric sweet potato remains in Polynesia suggests that the Polynesians may have made landfall in South America long before Columbus. (This theory is supported by linguistics: Kuumala, the Polynesian word for sweet potato, is closely related to kumara and cumal, the words for sweet potato in Quechua, the ancient Incan language still spoken by native people in the Andes.) Naturally, when Christopher Columbus finally made it across the eastern ocean, he brought sweet potatoes back to Europe; by the sixteenth century, Spanish explorers had introduced sweet potatoes to the Philippines, and Portuguese adventurers had ferried them to Africa, India, Indonesia and southern Asia. Beloved by Native Americans, sweet potatoes also were a significant source of nourishment for settlers and soldiers during the Revolutionary War.
And a good source of nourishment they are. Sweet potatoes are a very good source of fiber loaded with calcium, potassium, magnesium and phosphorus. Orange-skinned sweet potatoes contain a significant amount of beta carotene, which the body converts to retinol (vitamin A), necessary for vision and growth. It’s not surprising that a colonial physician referred to the sweet potato as the “vegetable indispensable.”
“Some people in the past have added marshmallows to this dish, which you may do at your own risk.”
More than half of all commercially grown sweet potatoes in the U.S. come from the southern states (primarily North Carolina). China currently is the world’s largest sweet potato producer, growing about 80 million tons—85 percent of the global crop—primarily to feed livestock and for industrial applications like biofuel and bioplastic. The second-largest harvest comes from Africa—that crop is used primarily for food.
Sweet potato production traditionally has been limited to tropical climates, but new, short-season varieties and techniques like soil warming have been developed that make it possible to grow them all the way north to the Canadian border. In northern zones, Georgia Jet, a popular Canadian variety, has proved to be reliable; Beauregard and Centennial also are popular. At Old Ford Farm in New Paltz, co-owner Becky Fullam says her sweet potatoes (Beauregards) are “a definite crowd pleaser,” relatively easy to grow and present few problems with insects or disease. However, harvesting can be a challenge: ”They have to be dug by hand and it is difficult to free the roots from the soil without piercing them with the fork,” Fullam says. “Mice also are a problem—-they nibble around the tops of many of the roots, making them unmarketable.”
Beauregards also are the variety of choice at Common Hands Farm, in Claverack, near Hudson, where they’ve proven to be a successful market crop. “They’re definitely a favorite,” says farm owner/manager Tess Parker. “If we want to do well in market, we bring the sweet potatoes. People are definitely looking for them.” Susan Paykin, farm manager of Common Ground Farm, in Wappingers Falls, believes her crop of Beauregards benefitted from the black plastic mulch used to keep weeds down and soil temperature up. “We lay a thin layer of plastic mulch down first, then transplant the sweet potato slips into the plastic,” she says. “The sweet potatoes appreciate the heat, and we don’t have to worry about weeding beds when the plants are small.
Sweet potatoes keep better than any other root vegetable if they’re stored properly. They should not be stored in the refrigerator or anywhere else, for that matter, where the temperature falls below 50˚F, as this will cause them to decay rapidly. They’ll last a month or two in a cupboard or bowl, but they’ll keep for up to a year if properly “cured.” The process is simple: Once harvested, brush them off (do not wash), store them at 85˚F for 2 weeks, then store at 60˚F for another 6 to 8 weeks. This curing process causes the tuber to form a “second skin,” which seals it and also intensifies the flavor.
Stories abound about when and where (and why) sweet potatoes became bound to a marshmallow topping—it wasn’t a widespread practice until industrialization made mass production of inexpensive marshmallows possible. (This is not to be confused with sweet potatoes glacé, a preparation that dates from the late eighteenth century in America.) Early in the twentieth century, the marketers of Angelus Marshmallows developed a booklet encouraging the use of marshmallows in both sweet and savory recipes, including the first documented appearance of mashed sweet potatoes with a marshmallow topping.
That was followed in 1930 by How Famous Chefs Use Campfire Marshmallows, an ambitious booklet produced by the company now known as Angelus-Campfire. Featuring recipes by some of New York City’s most prestigious hotel and restaurant chefs, the booklet included a half dozen recipes for sweet potato/marshmallow combos, including stuffed sweet potatoes á la Sanderson (twice-fried sweet potato puffs filled with a blend of marshmallow and cream) from Delmonico’s Chef Nicholas Sabatini, and sweet potatoes and pineapple Robert (layered sweet potato and pineapple slices with maple syrup and marshmallows) from the Ritz’s renowned Chef Louis Diat. The 1972 classic, James Beard’s American Cookery (rpt. Little, Brown, 2010; $35 hardcover), includes a recipe for a sweet potato casserole topped with brown sugar and maple syrup, to which Beard added a cautionary note: “Some people in the past have added marshmallows to this dish, which you may do at your own risk.”
But culinary traditions tend to die hard. In 1997, Thanksgiving fell halfway through American astronaut David Wolf’s four-month stint aboard the Russian space station. Though his foreign hosts graciously prepared a turkey dinner, Wolf, via radio, told his NASA bosses that he was “kind of missing those sweet potatoes with the marshmallows on top.”
A Yam is a Yam is Not a Sweet Potato
Sweet potatoes belong to the morning glory family Convolvulaceae, from the Latin word convolvere (to wind), a reference to the vines’ winding stem. Yams are the most well-known member of the family Dioscoreaceae of edible, tropical tubers—but they’re not even remotely related to sweet potatoes. BTW: The plain, everyday white, or Irish, potato is a member of the equally unrelated Solanaceae (nightshade) family.
Sweet potatoes are indigenous to Central and South America. Yams hail from west Africa (which produces 95 percent of the world’s crop) and Asia.
The word yam comes from the West African word nyami, which means to eat. When slaves from Africa first saw New World sweet potatoes, they erroneously referred to them as yams, and the label stuck.
Smooth-skinned sweet potatoes rarely weigh more than a pound and can be long and thin or short and fat, but always taper at the end. Yams have a rough, bark-like skin until cooked; offwhite, purple or red (but never orange) flesh; and they can grow to be over eight feet long and weigh well over 100 pounds (the largest yam on record tipped the scales at 230 pounds).
Sweet potatoes can be eaten raw; yams must be cooked (boiled, baked or fried) to remove harmful toxins. (In Africa and Polynesia, an extract of yam is used to poison arrows for hunting.)
The greens of the sweet potato plant are edible and quite nutritious, especially the darker varieties. (In Spanish cuisine they may be referred to as kamote or camote.) Yam greens are considered inedible.
Note: In some markets, particularly in the South, “yam greens” actually are mislabeled sweet potato greens.