Sweet Potatoes

November 6, 2021

Today’s Main Ingredient is Sweet Potatoes!
Host Mikki Uzupes learns about sweet potatoes from local farmer Dave Nonnenmacher of Nonnenmacher Acres outside of Honesdale PA, and executive chef Keegan Marchand from the French Manor Inn and Spa in South Sterling, PA. Nutritionist Carol Kneier adds how even starchy sweet potatoes contribute a healthy lifestyle.

About Sweet Potatoes

Sweet Potatoes are the edible roots of a plant in the morning glory family.
Ipomoea batatas 006
They are not related to yams, which are larger, less sweet, and have a tougher skin that looks a bit like tree bark. Potatoes, sweet potatoes, and yams are all in different plant families. However, they all have belowground plant structures called “tubers,” which function as storage organs for their plants, providing energy for regrowth. While sweet potatoes are true roots (“root tubers”), potatoes and yams are technically stems (“stem tubers”).

In tropical climates, sweet potatoes are a perennial, but in the U.S. in the North and East, short-season varieties are grown as an annual crop under black-plastic mulch. They do not tolerate frost. The trick is to plant them early enough for them to mature properly before an early fall frost, but not so early that they will be killed by a late spring frost. With lots of sun and warm soil, sweet potatoes are a fairly undemanding to grow; they have few natural enemies, and pesticides are rarely needed.

Getting Started in the Garden

Slips on a sprouted sweet potatoSweet potatoes are not grown from seed but from rooted sprouts called “slips.” Slips are available from garden centers, nurseries, and via internet catalogs.
Alternatively, you can start your own slips.

There are two ways of growing the slips—in soil or in water:

  1. The soil method:
    • In the fall, look for unblemished, smooth, organic sweet potatoes at the store or farmers’ market.
    • Store them in a cool (55°F), dark place until about 90 days before the last spring frost.
    • At this time, leaving half of the sweet potato showing above the soil, nestle the tuber in a container of moist potting soil with the sprouting end pointing up and the root end pointing down. The root end is usually fatter. (If you can’t tell the root end from the sprouting end, simply place the tuber in a warm place for two weeks. Buds will emerge, and you will know which end should go up.)
    • Water immediately and repeat again as needed to keep the soil damp, not soggy.
    • Maintain the soil and the room at 75°F to 80°F in sunlight; use a heating lamp if necessary.
    • In 4 to 6 weeks, the slips will be 6 to 12 inches long, with leaves and roots.
    • Remove the slips from the sweet potatoes, keeping roots attached. (If no roots formed, remove the slip and place it in water; roots will appear in 1 to 2 weeks.)
    • If it is too soon to plant, stand the slips in potting mix or sand and keep moist until planting time.
  2. The water method:
    Place the root end of the sweet potato in water to grow slips• Poke a small sweet potato with three toothpicks and place the skewered potato atop a glass so that the bottom (fatter end) is hanging into some water.
    • Within days, the sweet potato will start to sprout little white roots at the bottom and develop sprouts at the top. (Discard if the water gets scummy and the tuber starts to rot, and try again or use the soil method described above.)
    • Wait until the sprouts are a few inches long, then pull them from their base, freeing them from the sweet potato.
    • Stick the sprouts into their own jar of water and, once they form their own roots, at least a couple of inches long, they are ready for planting.

Site Preparation
• Choose a sunny spot with well-drained loamy to sandy soil. Sweet potatoes need plenty of air space in the soil for roots to reach down. If your soil is clay, rocky, or compacted, consider raised beds.
• Ensure that there is enough space for vines to spread out. Plantings should can be 10–18 inches apart—wider spacing produces larger potatoes—in rows spaced 36 to 60 inches apart. (The most common spacing is 12 inches apart in rows 36 to 42 inches apart).
• Mix in organic matter to a depth of 8 to 10 inches. Use fertile, well-drained soil. Add compost, perlite, and/or coconut coir to help build loamy soil and retain moisture. Avoid adding animal manure, including pelleted chicken manure; it can result in spindly and/or stained roots.
• Create raised mounds 6 to 8 inches tall and about 12 inches wide; this improves the drainage (very important) and gives the tubers a nice deep soil to develop in. (Otherwise you may end up with small, bent and forked sweet potatoes.)
• In the northern US or Canada, cover the growing area with black plastic or dark fabric mulch about 3 weeks before planting to help warm the soil.

How to plant sweet potato slips
• Plant slips on a warm, overcast day, when the soil temperature has reached at least 60°F.
• Break off the lower leaves, leaving only the top ones.
• Set the slips deep enough to cover the roots and the stem up to the leaves (sweet potatoes will form on the nodes), 10 to 18 inches apart.
• It is critical to thoroughly water the slips around the stems immediately after planting and then water generously for 7 to 10 days until the roots are well established.

Ipomoea batatas 002Care
• Side-dress the sweet potato plants 3 to 4 weeks after transplanting with 5-10-10 fertilizer. If you have sandy soil, use more.
• Weed the sweet potato beds regularly starting 2 weeks after planting.
• Avoid deep digging with a hoe or other tool; this can disturb the feeder roots.
• Water regularly, especially during mid-summer. Deep watering in hot, dry periods will help to increase yields. Late in the season, reduce watering to avoid cracking of the tuber’s skin in storage.
• Do not prune sweet potato vines.

Harvesting sweet potatoesHarvest
• Harvest when the leaves and ends of the vines have started turning yellow or about 100 days from planting.
• Loosen the soil around each plant (18 inches around, 4 to 6 inches deep) to avoid injuring the tubers. Cut away some of the vines.
• Pull up the plant’s primary crown and dig up the tubers by hand. Handle the sweet potatoes carefully, as they bruise easily.
• Shake off any excess dirt; do not wash the roots.
• Complete harvesting by the first fall frost.

Curing and Storing
After harvest, fresh sweet potatoes need to be cured to convert their starches to sugar, giving them their sweet flavor.
• Cure them for two to three weeks in a warm place. During this time, a second skin forms over scratches and bruises, and the flesh becomes sweeter and more nutritious.
• Curing continues during the first months of storage at cool room temperatures. So stored sweet potatoes, eaten in winter, are often the best ones of the year.
• To cure, store roots in a warm place (about 80° to 85°F) at high humidity (about 85 to 90%) for 10 to 14 days. A table outside in a shady spot works well. Arrange sweet potatoes so that they are not touching.
• After curing, discard bruised sweet potatoes, then wrap each one in newspaper to store.
• Carefully pack in a wooden box or basket. Store in a root cellar, basement, or a place with high humidity and a temperature of 55°F to 60°F. The sweet potatoes should last for about 6 months.

In the Kitchen

Although sweet potatoes and yams are different vegetables, they are treated the same way in cooking. Sweet potato varieties come in orange, pale yellow, purple, or white flesh. Orange ones are the sweetest.

Slips on a sprouted sweet potatoWorking with sweet potatoes
• Although they have a sturdy appearance, sweet potatoes are easily bruised; once bruised, spoilage can happen quickly. They also are not terribly good keepers, so plan to use them with a week of purchase.
• Storage: Keep them in a cool cupboard, if you have one, or on the counter. They can be refrigerated in a perforated plastic bag, but they don’t love the cold and they mustn’t be frozen.
• One-pound sweet potatoes (raw) yields 3 to 4 cups chopped or about 1 1/2 cups cooked & mashed. Allow at least 4 ounces for a serving.
• Scrub well before cooking. If you plan to eat the skins, look for organically-grown.
• If peeling raw, put sweet potatoes in a bowl of water to prevent oxidation; lemon isn’t necessary.

Sweet Potato FriesSweet potatoes are better boiled, baked, mashed, or puréed than pan fried, though they can be deep fried like French fries, or “oven fried.” Their sweet flesh can be puréed for both sweet or savory pies, puddings and breads.

Roasting: Choose sweet potatoes of similar size. Scrub well. For a whole 12-ounce sweet potato, roast at 400°F for 50 to 60 minutes until very tender when pierced with the tip of a knife. Or bake at a lower temperature (350°F) until tender. See the video halfway down this webpage.

Boiling: Cover whole potatoes in cold water and bring to a boil. Lower the heat and simmer until tender when pierced with a knife. Peel, then slice or mash and serve with butter, salt & pepper. Or peel and cut into chunks and steam over boiling water until tender.

Grilling: First, boil or steam sweet potatoes whole and let them cool completely. Then peel and slice into 1/2-inch-thick pieces. Brush with vegetable oil and grill, turning them 45 degrees after 7 minutes. Cook on both sides. Season with salt & pepper. Serve with barbecue sauce or Thai peanut sauce.

Broiling: Follow the directions for grilling and broil until sizzling.

Mashed sweet potatoMashing: Cook sweet potatoes using any of theses methods, then mash with 1 teaspoon grated orange or tangerine zest, the juice of an orange or tangerine, and butter to taste. Season well with salt and pepper.

Ingredients that pair well with sweet potatoes:
Butter, dark sesame and roasted peanut oil; ground ginger, nutmeg, allspice, cinnamon, ground cloves; orange, bits of pineapple, candied ginger; brown sugar, molasses, maple syrup; bourbon; toasted pecans or black walnuts; chilies.

Sugar, honey, or maple syrup as well as sweet spices can be added to intensify their sweetness. At Thanksgiving, they are often “candied” with orange juice and brown sugar.


Candied Sweet Potatoes – Serves 8
A traditional Thanksgiving dish beloved by many families.

6 tablespoons unsalted butter, divided
3 pounds sweet potatoes, peeled and cut into 1 1/2-inch pieces
3/4 cup packed dark brown sugar
1/4 cup fresh apple cider or orange juice
3 tablespoons bourbon (optional)
Kosher salt

Preheat the oven to 400°F.
Step 1 – Grease a 9-by-13-inch glass or ceramic baking dish with 1 tablespoon of the butter.

Step 2 – In a large saucepan of salted boiling water, blanch the sweet potatoes until barely tender, 8 to 10 minutes. Drain well. Spread them in the prepared baking dish in an even layer.

Step 3 – In a small saucepan, melt the remaining 5 tablespoons of butter with the brown sugar. Whisk in the cider and bourbon, season with salt and bring to a boil. Cook over moderately high heat, stirring, until the sugar dissolves, 1 to 2 minutes. Pour the mixture over the sweet potatoes and gently stir to coat.

Step 4 – Bake the sweet potatoes until tender and the sauce is syrupy, 35 to 40 minutes.

Note: The recipe can be prepared ahead (through Step 3) and refrigerated overnight, but bring to room temperature before baking.

Download Recipe

Beef and Sweet Potato Stew – Serves 6

3 Tablespoons vegetable oil, divided
4 cloves garlic, finely chopped
1 large onion, cut into small wedges
About 2 lbs beef stew meat, trimmed of fat, cut into 1 1/2-inch pieces
1/2 cup all-purpose flour
2 cups beef broth
1/2 cup water
2 teaspoons chopped fresh rosemary leaves
2 teaspoons salt
1/2 teaspoon pepper
2 dried bay leaves
1 pound parsnips, peeled, cut into 2×1-inch pieces
2 pounds sweet potatoes, peeled, cut into 1-inch chunks
Additional chopped fresh rosemary, if desired

Preheat the oven to 300°F.
Step 1 – In 12-inch skillet, heat 1 Tablespoon of the oil over medium-high heat. Cook garlic in oil 1 minute or until golden. Place the garlic along with the raw onion wedges in a 4-quart Dutch oven.

Step 2 – In resealable food-storage plastic bag, place beef and flour; seal bag and toss to coat. In same skillet, heat 1 tablespoon oil over medium-high heat. Add half of beef; brown on all sides. Transfer beef to Dutch oven. Repeat with remaining tablespoon of oil and beef.

Step 3 – Add broth to skillet; heat to boiling, scraping bottom to loosen brown particles. Pour this over beef mixture. Stir in water, 2 teaspoons rosemary, the salt, pepper, bay leaves and parsnips.

Step 4 – Cover and bake for 3 hours. Stir sweet potatoes into stew. Bake covered for another hour longer, or until beef and vegetables are tender. Remove bay leaves before serving. Garnish with additional rosemary.

Download Recipe

A version of this recipe using an Instant-Pot/pressure cooker is available at
Or, using a Crock-pot/slow cooker at

Old-fashioned Grated Sweet Potato Pudding
Southerners like sweet potatoes baked, boiled, steamed, mashed, candied, made into croquettes, and baked in pies. This pudding is a traditional Southern dish.

Nonstick cooking spray
1 pound (2 large or 3 small) sweet potatoes, peeled and cut into chunks
1/2 cup dark brown sugar
1/2 cup light brown sugar
3/4 teaspoon salt
2 teaspoons ground ginger
2 Tablespoons cornmeal (white or yellow)
1 large egg
2 large egg yolks
1 cup heavy whipping cream
1 Tablespoon pure vanilla extract

Preheat the oven to 325°F.
Step 1 – Spray a 9 x 13 x 2 1/2-inch casserole with nonstick cooking spray.

Step 2 – In a large saucepan of salted boiling water, blanch the sweet potatoes until barely tender, 8 to 10 minutes. Drain well. Spread them in the prepared baking dish in an even layer.

Step 3 – Finely chop by hand or pulse in a food processor in several batches until the sweet potatoes are the texture of large rice. Mix the sweet potato, brown sugars, salt, ginger and cornmeal in a large mixing bowl. Stir in the egg, egg yolks, cream, and vanilla.

Step 4 – Pour into the casserole and bake for 15 minutes; then stir from the outside to the middle (see note). Continue baking and stir again after 10 minutes. Cook until lightly browned and just set, about 40 minutes total. Serve hot or at room temperature.

Note: The edges of a baked casserole tend to overcook and get dry before the center is done. Stirring twice during baking solves this problem.

Download Recipe

Sweet Potato Pie – Serves 6 to 8

1 pie crust (deep 9-inch or 10-inch regular)
3 medium-to-large sweet potatoes
1 stick softened butter
1 cup firmly packed brown sugar (light or dark)
3 eggs
1/4 teaspoon salt
1/2 teaspoon vanilla extract
A mix of spices to total 1 1/2 teaspoons: cinnamon, cloves, nutmeg, ginger, allspice, and/or mace
1 cup canned sweet (condensed) or evaporated milk or half-and-half

Preheat the oven to 350°F.
Step 1 – Bake or boil whole sweet potatoes until tender. When cool enough to handle, peel and mash them to make 3 cups.

Step 2 – Cream the butter with the brown sugar until smooth. Beat 3 eggs and combine with the butter/sugar mixture. Add salt, vanilla extract, and your combination of spices. Stir in mashed sweet potatoes. Add canned milk or half-and-half and beat mixture well.

Step 3 – Pour into the pie shell. Bake at 350°F for 50 minutes to 1 hour or until the center is firm.

Download Recipe

For more sweet potato recipes see these websites:

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Today's Main Ingredient is sponsored in part by:

Greater Pike Community Foundation
Overlook Estate Foundation
Wayne-Pike Farm Bureau

Thanks also to Fertile Valley and Wolfe Spring Farms for their sponsorship of the BoldGold radio station broadcasts.

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