Sweet Potato, Another American
The sweet potato (Ipomoea batatas) is another of the native American plants found by Columbus and his shipmates. Although it was probably found on various islands of the West Indies on some of the earlier voyages, it is not definitely mentioned in their records until the fourth voyage.
In the islands off the coast of Yucatan and Honduras the sweet potato was called axi and batatas or betatas by the natives; in 1514, Peter Martyr named nine varieties that grew in Honduras. It was taken to Spain about 1500 and several kinds were cultivated there by the middle of the 16th century, including red, purple, and pale or "white" varieties.
Cultivation of sweet potatoes was tried unsuccessfully in Belgium in 1576. John Gerarde of London, claimed that in 1597 he grew the plant in England (probably without much success) and that it was known in India, Barbary, and other hot regions.
Early Spanish explorers are believed to have taken the sweet potato to the Philippines and East Indies, from which it was soon carried to India, China, and Malaya by Portuguese voyagers. The original introductions from America into the Pacific and Far East were so unobtrusive that the origin of the plant was long overlooked, many believing it native to southern and southeastern Asia.
Especially Important in Tropical Areas
The sweet potato has become far more important in subtropical and tropical areas than has the Irish potato because it thrives in a hot, moist climate, while the latter requires a cool climate. Thus it has never become popular in Europe and it still is little known even in the warmer Mediterranean areas. It is important in the warm Pacific islands, the East Indies, India, China, and is now the third most important food crop in Japan.
Apparently the sweet potato was introduced to Kyushu from China some time around 1700, by way of the Ryukyu Islands. In southern Kyushu today it is commonly called kara-imo, meaning Chinese potato; but in most of the other parts of Japan it is called satsuma-imo (Japanese potato). The relatively recent introduction of the sweet potato into Japan seems in itself a good argument against its Chinese or other Asiatic origin.
In the past 25 years, plant breeders in Australia and in the warmer parts of the Soviet Union have taken great interest in its food-producing possibilities and have sought to develop its culture on a large scale.
Sweet potatoes were cultivated in Virginia in 1648, possibly earlier, and are said to have been taken into New England in 1764. They were grown by the Indians of our South in the 18th century, but we do not know how much earlier. In the South today they are generally preferred to Irish potatoes as a staple food; in the North the reverse is true.
Generally speaking, the northern consumers prefer the so-called "dry-fleshed" type of sweet potato, such as Big Stem Jersey and Little Stem Jersey, while the southerners prefer the "moist-fleshed" type, such as the Porto Rico and Nancy Hall varieties. A strange fact about these two types of sweet potato is that the "dry-fleshed" ones have more water in them than the "moist-fleshed" ones do!
The soft, rich, "moist" varieties are erroneously called "yams" in the United States. This confusion in names is unfortunate, since the yam is an entirely different plant, belonging to the genus Dioscorea. True yams are still a curiosity in the United States.
The flesh of most sweet potato varieties is white or nearly so, although in the United States we prefer yellow or orange-fleshed varieties because of their valuable carotene (provitamin A) content. Some kinds have purple flesh, but they are not grown here.
Skin colors range from nearly white through shades of buff to brown or through pink to copper, even magenta and purple. Americans are prejudiced against the purplish skin colors because certain "red" varieties formerly grown here were of poor quality.
Many Fed to Livestock in South
In our northern States the sweet potato is used only as human food, and to only a small extent. In the South a large part of the crop is fed to livestock, and efforts are being made to breed varieties that will produce large yields cheaply enough to permit their culture entirely for stock feed or industrial use.
The sweet potato generally contains more starch than the Irish potato, and the starch has properties that are especially useful in many food products and manufacturing processes. As yet, however, the growing and handling of the crop is too costly for it to be produced especially for starch manufacture.
Sweet potato candies, ice cream, cookies, and related delicacies prepared from this vegetable are not yet widely known, but they are surprisingly good.
Except in the Tropics, the sweet potato rarely flowers under ordinary field conditions and more rarely sets seed. Thus sweet potato breeders in the Temperate Zones, as in Japan or the United States, must resort to special methods of training and greenhouse culture, or even send their parent varieties to the Tropics for flowering and hybridization.