Plant Answers  >  Sweet Potatoes

Sweet Potatoes

If you had to be isolated on a tropical island with the vegetable of your choice, what would it be? Your best bet would be Ipomoea batatas. Ipomoea batatas is a vegetable that looks like a morning glory, is native to North America, enjoys hot weather, and is one of the most nutritionally complete foods known. This vegetable can be boiled, baked, browned, fried, and candied. It can be used to make biscuits, bread, muffins, croquettes, pies, custards, cookies, or cakes.

The Incas of South America and Mayas of Central America grew several varieties, calling the plant cassiri. One variety was grown for food and other varieties were grown to supply their artists with coloring materials to use in their plants. It was the most important, single food in bringing Americans through such trying periods as the American Revolution, the War Between the States, and Reconstruction. During such periods, it was said to be "the indispensable vegetable."

Because Ipomoea batatas does grow similar to a morning glory, it needs plenty of room and is probably not adapted for small garden culture. I have had success growing this delicacy in hanging baskets and bushel containers, but vines must be trimmed periodically to keep them in bounds. Trimming makes the plant branch and become thicker, which produces a more decorative hanging basket or container plant.

If you have not guessed by now, Ipomoea batatas is the scientific name for the sweet potato. I said sweet potato-not yam. I doubt if anyone reading this column has ever seen a true yam. This author hasn't! Yam is the term that has been erroneously assigned to smaller sweet potato roots. The name is a gimmick that supposedly conveys a sense of quality about the common sweet potato. However, the true yam is of a different genus, Dioscorea, and is a monocot (having a one?leaf embryo). Farmers plant sweet potatoes, but by the time the harvested product reaches the grocery store, it has become yams! Amazing!

Sweet potatoes are hot weather lovers. Not only are they "lovers," but they are also "needers" that will be damaged or killed by the lightest frost. The crop should be dug before the first hard frost. If roots are allowed to severely chill, the eating quality and storage properties of 75% of all harvested crop will be affected.

Probably the best time to harvest for storage is after the leaves show a slight yellowing, indicating that growth is slowing, and before or very soon after the first light frost. The earliest ones planted generally should be harvested first. The digging should be done if possible when the soil is dry and the temperature fairly high. Much less heat is required in curing if sweet potatoes are harvested and cured when the weather is still fairly warm.

The root of a sweet potato is covered by a thin, delicate skin that can be very easily broken. Striking the roots with harvesting implements or throwing them into containers injures this skin. The sweet potatoes may be cut or bruised if they are placed in crates or other containers that have sharp edges or rough places on the inside or if the packages are roughly handled.

If a sweet potato is cut or bruised during harvesting or handling, a heavy, milky juice exudes from the injured cells. This juice dries in a few hours and may appear to have closed the wound but actually several days are required for the growth of new cells that protect the interior cells from infection. The dried juice on the surface of a wound on a sweet potato is in itself no appreciable protection against rotting. To heal wounds of harvesting, sweet potatoes must be cured. In general, the following curing periods are suggested for sweet potatoes harvested at about the time of the average date of the first frost:
curing temperatures 85 degrees F.: 4 to 7 days
80 degrees: 8 to 10 days
75 degrees: 15 to 20 days
70 degrees: 25 to 30 days.

Curing too long results in excessive sprouting. Cured potatoes are sweeter tasting and will keep longer in storage since the skinned and bruised areas are allowed to heal over. After curing, hold potatoes at about 60 degrees F., with as high humidity as possible. DO NOT STORE SWEET POTATOES IN THE REFRIGERATOR. Short periods of a few hours at temperatures somewhat lower than 55 degrees may not cause alarm, but longer periods of low temperature should be avoided because of possible chilling injury, or possible damage from certain types of decay which may soon develop in the injured tissues and which are more likely to develop at temperatures below the given range. Non-cured sweet potatoes are more susceptible to cold injury, or chilling, than cured ones. Non-cured roots left at a temperature of 50 degrees or lower for only a few days may be seriously damaged. The general symptoms of cold injury are increased decay and internal discoloration that may show up before or after cooking. Under the temperature conditions mentioned above, properly cured roots should keep satisfactorily for 4 to 6 months.

Texas ranks only fourth in production of this vegetable delicacy, primarily because of the small weevil insect. This weevil is either imported in infested plants or, in the case of much of South Texas, is native. The weevil lays eggs in the roots when ground cracks occur around the enlarging system. Then, when our root vegetable delicacy is harvested, we have meat and potatoes both! Some folks don't appreciate this combination! Unfortunately, an answer to the problem has not been found. Gardeners who use a lot of organic matter or mulches around the vines keep ground cracks filled and thus have fewer problems with weevil infestations. However, once a garden has been infested, sweet potato production should be abandoned.

So, if you planted sweet potatoes last spring, now is the time to harvest and cure the roots. If you enjoyed the pumpkin pies of Halloween, you will love the sweet potatoes of Thanksgiving. Sweet potato consumption in the U.S. is five to six pounds per capita-probably on all on Thanksgiving Day! Sweet potatoes are better for diabetics than Irish potatoes because sweet potatoes are roots, and regular potatoes are tubers, meaning they store carbohydrates that can be turned into sugar.

For more information about sweet potatoes, the yam versus sweet potato controversy, and some wonderful recipes, see:


Sweetpotato Culture




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