Set the Table with Sweet Potatoes

Sweet Potato

Written on

September 01 , 2011

In prehistoric cave sites in Peru, scientists have found remains of sweet potatoes dating back to the dawn of agriculture 10,000 years ago. It is one of the oldest vegetables grown by humans. Yet even with that amount of history in every velvety, sensuous mouthful, the sweet potato is also a plant of the future, and may be a very important plant indeed for Vermont’s future. We are witnessing the arrival and adaptation of a new staple food crop to the Northeast—a rare and exciting event.

A perennial vine in the same genus as morning glories, the sweet potato,Ipomoea batatas, is native to the American tropics. It is not related to the regular potato, nor is it related to the true yam, which is native to Africa and Asia and belongs to the monocot family Dioscoreaceae. Not to be daunted by genetic heritage, however, Americans have managed to thoroughly confuse the names “yam” and “sweet potato” to the point where the average person doesn’t have a clue which one they’re buying. The muddle began back in the mid-1900s when the orange or “soft” fleshed sweet potato was introduced to America. Until then, the name sweet potato referred to a tuber with white, firm flesh. To distinguish the new orange arrival, people started calling it a yam, presumably because it vaguely resembled the true yam. Confusion has reigned ever since.

In the U.S., most sweet potatoes are grown in the southeast, but early maturing cultivars can be grown as an annual crop here in the northern U.S., requiring early starting (see sidebar). Sweet potatoes prefer hot, dry weather once the vines are established and some local farmers feel that the vegetable will do increasingly well here in the future as climate change warms the Northeast. Unfortunately consistency is not a word that is particularly associated with climate change; more appropriate words might be erratic, unpredictable, or unknown. Weather with radically alternating spells of hot and cold slows the growth of sweet potatoes. Too much rain, too much irrigation, or poorly drained soil can prevent proper root formation, resulting in long stringy tubers instead of short plump ones. Heavy rain during the last few weeks before harvest, especially after a long dry spell, can cause the roots to split, and proper curing can be a problem in the cool, wet New England autumn. Add to this the complexities of starting the seedlings, and the prospects of a thriving local sweet potato industry appear a bit less scintillating. Still, they might be a better bet than most grains for locally grown starchy food.

In 1992, the Center for Science in the Public Interest compared the nutritional value of sweet potatoes to other vegetables; it ranked highest, rich in complex carbohydrates, fiber, beta-carotene, vitamin B6, and vitamin C. White sweet potato contains iodine. To get the best absorption of beta-carotene, eat your sweets with some fat. A little butter or olive oil works fine. And the culinary possibilities of sweet potatoes are nearly limitless. The young leaves and shoots of the sweet potato are a popular vegetable in many countries. Sauté, steam, or boil as you would any greens and season to taste. The tubers can be transformed into products ranging from flour to wine. Global creative uses of the tuber include sweet potato cellophane noodles (Korea); sweet potato tong sui soup (China); tempura (Japan); and sweet potato butters, dips, and spreads (Vermont).

Lisa Johnson of Norwich is the founder and “Y’ambassador” of Yummy Yammy, a Vermont company that sells five kinds of sweet potato dips that are delightfully versatile for culinary use. The idea for the business grew from her desire to get more sweet potatoes into her family’s meals, and to find an efficient way of doing that. She started cooking them ahead of time and “suddenly got the idea that nobody was selling sweet potato products.” Especially not savory ones.

In October 2009, she sold her first container of Yummy Yammy spread at Dan & Whit’s in Norwich. Since then, her business has “exploded.” She now supplies six additional stores: the Hanover, Lebanon and White River co-ops, the Lyme Country Store in New Hampshire, the WREN store in Bethlehem, and BG’s Market in Hartland. She has started hot-packing her products in glass jars for a stable shelf life and has moved her manufacturing operations to the new Vermont Food Venture Center in Hardwick. She offers her products online and is about to go national with sales.

Lisa sources local sweet potatoes whenever possible but there is a limited supply, mainly because few Vermont farmers are growing sweet potatoes. Plus, Johnson has strict criteria for quality and needs jumbo size tubers for efficient processing. She roasts the tubers whole and slips off the skins while hot. Roasting helps preserve the flavor and nutrients.

“I think sweet potatoes grown in New England are really great quality,” she says, adding that she would like to see more New England farmers growing them and would like to see an entire industry built around local sweet potatoes. If her business continues along its growth curve, she may create a substantial demand. Lisa also has dreams of an annual yammy festival, perhaps at Halloween. The Yummy Yammy website (yummyammy.com) includes many ideas for how to use the dips and short, fun, and instructional videos.

Fertile Fields Farm in Westmoreland, NH, has been growing certified organic sweet potatoes for about five years. This year they have four varieties on a quarter acre. They like to try new varieties; the ones most likely to succeed, says farmer Lori Schreier, are those that need 100 days or fewer of growing season. Fertile Fields Farms sweet potatoes are available at the Brattleboro Farmers’ Market starting in October and at the Post Oil Solutions Winter Farmers’ Market in Brattleboro in November and December.

Stock up on local sweet potatoes while they are in season and you’ll have the base for months of fun in the kitchen. Chunks of sweet potatoes make a rich curry when infused with coconut milk, raisins, cashews, and Indian spices. Pair them with local white beans and veggies for a hearty, warming chili. Whole baked sweets are great for lunchbox surprises, being just as good cold as they are hot. And sweet potato fries are a classic and couldn’t be easier—just slice, toss with olive oil and your choice of spices or herbs, and bake in a single layer, turning once until golden. Use puréed sweets as you would pumpkin in pies, breads and cookies. You can even eat them raw like carrot sticks or shred them into salads. If your tubers start to look weary as the season progresses, make a big batch of something yummy (stew, soup, baked treats) or just cook them up plain and pop in the freezer.

For a sweet and spicy start to your day, try my original Jamaican Breakfast; it marries a large percentage of local sweet potatoes with a relatively small percentage of non-local ingredients for an exotic taste experience.

Steam chunks of local sweet potato until tender (for a less sweet dish, use half sweet potato and half regular local potato). Add chunks of banana (broken, not sliced) and cubes of steamed or fried local tofu (optional). Season generously to taste with cumin, coriander, garam masala, salt, and cayenne. Toss with a little local sunflower oil or melted butter and reheat gently with a little coconut milk. Serve sprinkled with shredded unsweetened coconut and coarsely shredded Brazil nuts.

Growing Backyard Sweet Potatoes

Recently, locally grown sweet potatoes have become popular in the north, where early maturing cultivars are treated as an annual. You can grow your own; the propagation technique is interesting and unusual. Like tomatoes (also a tropical perennial in the south), sweet potatoes need to be started inside early, say, in March. These instructions are based on information from Sylvia Davatz of Solstice Seeds in Hartland.

Choose organic tubers (non-organic ones won’t sprout) of an early maturing variety such as Georgia Jet or Beauregard. Use toothpicks to suspend the tuber vertically in a glass of water with 1/3 of tuber submerged. If you can determine which end of the tuber was attached to the plant (the end that’s broken), this end should be pointing up. When the sprouts or slips get to be a minimum of 2–3 inches long (longer is better), gently break them off the tuber right at the base. Put the slips into water and let them root. When well rooted, pot them up in small pots until the weather and soil have thoroughly warmed up (usually late June), then transfer them to the garden. The vines spread quickly—shading out weeds—and have few pests.

In fall, if you like, you can take cuttings from your vines in the garden before they are damaged by frost. Root the cuttings in water, plant into pots, and grow inside for the winter. The growth will slow dramatically but will pick up in spring; then you can pinch the plants to make them branch and use them for a new batch of cuttings to root and plant in the garden. Growing your own means you can also have fun eating the leaves and shoots!

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