When the Spanish explorers first came to the New World they were searching for an ocean route to India and its fabled treasures of gold, silver, spices and jewels. They found them on these two new continents, North and South America, but they found many other things far more valuable, including three of the world' s most important food plants: corn, the white or Irish potato, and the sweet potato.
Being a tropical plant, the sweet potato probably was found before the Irish potato -- by Columbus in the West Indies, by Balboa in Central America, and by Pizarro in Peru. Like corn, it was not found growing wild, but it had been cultivated by the Incan and pre-Incan
races for thousands of years. They had developed many varieties, as is shown by their ancient pottery. In most places in Latin America, the sweet potato is called "camote", but the Incans called it "batata" and that is apparently the origin of our word "potato".
The sweet potato was carried back to Spain and thence to Italy, from where it spread to Austria, Germany, Belgium and England before the first Irish potatoes arrived. It took 200 years for the English to accept Irish potatoes as being fit for human food, but the sweet potato immediately became a rare and expensive delicacy. Now it is widely grown in Asiatic lands, including Japan and southern Russia, in the warmer Pacific islands, in tropical America, and in the United States as far north as New Jersey.
Outside of the tropics, sweet potatoes thrive only in the warmer temperate climates, and do best in a loose sandy soil that is well drained. They produce seed only in the tropical climates. In northern climates, new plants are obtained by planting roots, or cuttings of the vines, in beds. The sprouts that form are pulled and transplanted to fields one sprout to a "hill". Once well started, they require little moisture and, unless attacked by the numerous diseases and insect pests to which they are subject, develop many potatoes in each hill.
Sweet potatoes produce more pounds of food per acre than any other cultivated plant, including corn and the Irish potato. More nourishing than Irish potatoes because they contain more sugars and fats, they are a universal food in tropical America, and in our southern states where they are baked, candied, boiled and even fried. Vast quantities are canned for consumption in the United States. Of the 200 or more varieties there are two main types. The "Jersey" and related varieties having dry mealy flesh are favored in the northern states. The other type, more watery but richer in sugar and more soft and gelatinous when cooked, is favored in our southern states where they are called "yams". The true yam, however, originated in China and is a different plant related to the lilies. The Irish potato, believe it or not, belongs to the Nighshade Family.
The sweet potato botanically, belongs to the Morning Glory family. There is another member of this family, a native weed known in Illinois and Indiana as "wild potato vine", "wild sweet potato" or "man-of-the-earth", with an enormous fleshy root much esteemed as food by the Indians. Above ground, the sweet potato develops creeping twining vines with pink or purple blossoms like those of the morning glory. Its thick starchy roots develop into the tubers we call "sweet potatoes". These contain carotene, the chemical which produces the orange colors in autumn leaves and in carrots. The Indians in Latin America make a beautiful permanent red dye from the mixed juices of limes and sweet potatoes.
Said the sweet potato to the Irish potato: "You're no potato! I yam."