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Sweet Potatoes, by Rashaun Ellis

Picture of 8 varied varieties of sweet potatoes, from crop stories No.4

Roots: Sweet Potatoes

by Rashaun Ellis

Peru is considered the birthplace of the potato, most likely in Altiplano near Lake Titicaca. Archaeological evidence points to a history of Peruvian cultivation going back to 1580 BC. From Peru, according to anthropological theories, early ocean explorers transported tubers to South Pacific islands.

Spanish explorers witnessed cultivation of several different potato varieties via the Incas, and took both “Irish” and sweet potatoes back to Europe with them. Before then, Europeans were unaware of the sweet potato, but they soon became highly sought after by sweet-toothed Western Europeans. In John Gerard’s 1597 book, The Herball or Generall Historie of Plantes, he recommends roasting them and flavoring them with wine, vinegar, and/or salt. He also advocated boiling them with prunes. Their sweetness earned sweet potatoes a reputation as an aphrodisiac amongst the upper-class. The 1620 publication of The Book of Cookerie by Thomas Dawson included a recipe for “a tarte to cause courage either in a man or woman,” with the main ingredient being sweet potato (simply known as a “potato” to Europeans at the time).  Henry VIII enjoyed spiced sweet potato pies.

Root vegetables were an important source of subsistence nutrition for native peoples in the Americas. They grew well in poor soil, could handle cold weather, and had a long shelf life, especially when naturally dehydrated and mashed into a substance called chuño, as practiced by the Queachua peoples of the Andes moutains which can be stored for up to ten years.  Sweet potatoes were most likely roasted for daily consumption, and modern day agrarian families in Peru can still eat up to five pounds of potatoes, sweet or not, in a day.

In North America, sweet potatoes were a primary source of nutrition for enslaved Africans, who wrapped the tubers in leaves and roasted them over open fire. Later, for free blacks who became self-employed farmers, sweet potatoes were a livelihood and a life-giver. Their heartiness made them perfect for travelers to carry over long distances. Slowly, they began to integrate into the popular cuisine of white communities. The plant’s culinary uses went beyond roasting, dehydrating, boiling, and pounding. Floridian pioneers roasted sweet potatoes until they were very brown and dry, then ground them into meal and steeped them in hot water for a tasty, but caffeine-free, coffee substitute.

Commercial sweet potato production began in earnest in the 1930s, and it served as a fortune-builder through World War II. Sweet potato yields in the United States were strongest in 1932, during the Great Depression, serving as hearty, nutritious option for distressed communities. One million acres were harvested that year, whereas only one-tenth of that amount was harvested in 1996. The post-war exodus from farms into cities shifted sweet potato power from the United States. Today, China has become the world’s number one sweet potato grower, accounting for 80 percent of harvests. The United States ranks eighth internationally, behind many African countries and Vietnam.

The post-war decline in U.S. sweet potato farming and consumption began to reverse in the early 2000s, as doctors and nutritionists drew attention to the vegetable’s health value. Sweet potatoes have a wealth of beta carotene, fiber, and vitamins A and C. Though they can be richly sweet, these potatoes rank low on the glycemic index. Declared a “superfood,” even fast food restaurants use sweet potatoes as a heart-smart alternative. And it’s not just culinary interest driving this boom, but a diversity of uses. Starch, animal feed, and biofuels are major drivers.

Over 400 cultivars of ipomoea batatas are currently recognized. Each one possesses its own characteristics, with skin color ranging from volcanic red to rich cadmium. In the field, they can grow squat and round, dark and long, or pale and twisted. They can be firm or soft in flesh. Some are heirloom varieties, grown for generations. Others are born in labs, generated by academic researchers in Louisiana or North Carolina. Some varieties are purple with deep hues that can stain a shirt. Others can be surprisingly dry or bitter, pock-marked by eager sprouts. Still others are bred for supermarket perfection, sweet and without blemish, easy to grow and keep.

Historically, the botanical classification of a sweet potato followed its foliage. From round leaves to heart-shaped ones to split or lobed versions, with blue and purple veins streaking through speckled leaves. While the greens of most Irish potatoes are either poisonous or unappetizing, the vines and leaves of sweet potatoes have a high nutrient value. Sweet potato greens are a large part of African cuisine alongside their native yams.

West African cuisines incorporate sweet potato greens in soups and stir-fry style recipes from Guinea. In the United States, nutrient-rich leaves and shoots can be harvested several times a year, though their shelf-life is short. Farmers are the best source.

Sweet potatoes are members of the morning glory family, convolvulaceae, as indicated by their beautiful purple and white blooms. The African yam is not related to the sweet potato at all, though in the United States the names sweet potato and yam are used interchangeably.  Some historians attribute this to enslaved African using their native language to describe the sweet potato found in the new world (nyami means “yam” in certain African dialects). Yams are long, heavy, unsweet, white-fleshed tubers.  They, unlike the sweet potato, must be cooked to be safely eaten. Yams are often roasted or dried, then pounded into powder that is then made into a paste or pudding to be eaten.

Before it can be consumed, a freshly harvested sweet potato must be cured. Early southern farmers would uproot the plant, leaving the tuber exposed on top of the soil for a few days.  This minimized some of the root’s moisture and significantly decreased spoilage. But this flawed method hurt yields, so farmers began to cure their crop in tobacco barns. The structure guarded against weather and animals, and a tobacco barn’s breezy construction, with air flowing freely between gaps in wall plans, were ideal. Eventually farmers built sweet potato barns, or “curing houses,” specifically for this purpose.

Sweet potato barns became as ubiquitous as water towers and cotton fields in the South.  Lonely barns sitting out in the middle of fields are a common sight in historic farming communities. They blend into the landscape, a dot on the horizon that even locals stop noticing after a few years. Many have dissolved back into the earth. Along the eastern shore in states like Delaware, Maryland, and Virginia, sweet potato curing barns have been added to the National Register of Historic Places, and many have been restored.

Since the 1970s, North Carolina has led production of sweet potatoes in the South. That’s when farmers began switching from tobacco growing to other crops. North Carolina specializes in sweet potato varieties like Covington, Garnet, and Beauregard and provides over 50 percent of America’s sweet potato crop, with California and Mississippi coming in second and third. Those three states account for 90 percent of the nation’s sweet potato crop. 

Varieties delivered to supermarkets stray very little from industry standards like the Beauregard, but a trove of heirloom varieties are available from market farmers. Slips of Brinkley White and Arkansas Red ship each season from historically-minded seed preservation companies. For farmers, these varieties represent a low-stress crop that sells well over a long period of time. There’s no quick wilt after harvest. For eaters, heirloom varieties offer options in color and taste, and diversity of flavor that goes well beyond candied yams and sweet potato pie. 

From: Crop stories No.4