How to Grow Sweet Potatoes

MOTHER'S vegetable garden shares how to grow sweet potatoes, including the history and horticulture of the sweet potato, what, where, when and how to plant, pests, and how to harvest and store sweet potatoes.

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    Sweet potatoes are one of the few vegetables capable of providing the full nutritional needs of human beings, and they're delicious boiled or baked, whole or mashed, and in casseroles, puddings, breads and soups

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MOTHER'S vegetable garden shares how to grow sweet potatoes. While white-potato foliage is toxic, that of the sweet potato can be stir-fried. 

How to Grow Sweet Potatoes

AS A CHILD, ONE OF MY FAVORITE after-school snacks was a warm-from-the oven baked sweet potato. My sisters and I would slit them open, pour in some melted butter, and spoon out the succulent yellow or orange flesh, scraping the last satisfying bite from the skins. Our mother (probably wisely) never pointed out that these garden grown treats were also good for us. Though vitamin content can vary with different varieties, an average-sized tuber contains a whopping 15,000 international units of vitamin A and about half as much vitamin C as an orange. Added to that are worthwhile amounts of protein, calcium, magnesium, iron and carotene, and practically no fat. In fact, sweet potatoes are one of the few vegetables capable of providing the full nutritional needs of human beings, and they're delicious boiled or baked, whole or mashed, and in casseroles, puddings, breads and soups. They can substitute for pumpkin in pies and are used to make candies, ice cream and cookies. (For an unusual salad, grate and mix raw sweet potatoes with green peppers, cucumbers and nuts.) In Japan, where sweet potatoes are the second most important crop, they've long been a popular ingredient both in stir-fry and tempura dishes.

The sweet potato (Ipomoea batatas) probably was first cultivated in Peru, and four varieties, along with sweet potato bread, were served to an impressed Christopher Columbus on his fourth voyage to the West Indies. In the sixteenth century, these vegetable natives of Central and South America were introduced to Spain, but they were not grown extensively in the southern United States until the mid-eighteenth century. Today, the crop is found in many tropical and subtropical regions—Polynesia, the Philippines, New Zealand, Australia, Africa, Asia and even in southern parts of the USSR. In most of Europe, however, this heat- and moisture loving plant never gained the popularity of the botanically unrelated Irish potato (Solanum tuberosum). The sweet potato is, in fact, a close kin to morning glories, and in tropical climates, it produces small white, pink, red-purple or pale violet flowers. In more temperate regions, the quick-growing vines rarely flower and those that do seldom produce seeds. Even so, it's wonderful to watch this vegetable grow, and because it thrives during the hottest days of summer, it can be one of the prettiest plants in the August garden. It's also beautiful trailing from a hanging basket and can be used as a temporary ground cover. In large containers, sweet potatoes can be grown—and harvested—as patio plants.

What Varieties of Sweet Potatoes to Plant

Because sweet potatoes are hot-climate natives, they are extremely sensitive to frost. Many varieties require 150 to 170 days of warm growing weather, though some types—the popular copper-skinned, high-yielding Centennial and the good-storing New Jewell, for example-mature in 90 to 100 days. The compact Bush Porto Rico does well in small gardens or on trellises or wires in greenhouses. Old Gold, whose flavor continues to improve for some time after harvesting, is a favorite variety for storing, while other cultivars are prized for their disease and pest-resistance. Nancy Gold, for instance, is resistant to soft rot, while Heart-0-Gold resists the root-knot nematode and All gold not only resists stem rot but also can ward off a viral disease called internal cork.

Most sweet potatoes have reddish tan skins and creamy yellow to deep orange flesh and are classified as "moist" or "dry," terms that describe the eating texture of the flesh. Moist, deep orange types—like the soft-fleshed, sugary, good-storing Porto Rico (150 days)—are sometimes called "yams" because of their resemblance to the true yam (Dioscorea alata or D. sativa), an African plant that can be raised only in tropical climates.

When to Plant Sweet Potatoes

Sweet potatoes are grown from slips—sprouts taken from the tubers. While sweet potato slips can be purchased from nurseries, seed houses and garden supply stores, it's easy to propagate them yourself. First, locate some tubers that haven't been treated or waxed to prevent sprouting. Then, some six to eight weeks before planting time, half bury them in a pan or box of rooting medium (moist sand, sawdust or chopped leaves will do) or suspend a potato with toothpicks halfway into a water-filled jar. To be successful, keep these potato parents moist and at a temperature between 75 degrees Fahrenheit and 80 degrees Fahrenheit. (The Japanese use the warmth of miniature compost heaps to start potato slips.) Approximately a month later, the first shoots will appear. When they're about six to nine inches long, cut them from the parent potato and remove and dispose of the bottom inch from each slip, because this particular segment sometimes harbors disease organisms.

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