The sweet potato is the true storage root of Ipomoea batatas, a member of the morning glory family. It is native to northern South America, and may have reached Polynesia in prehistoric times. Columbus brought the sweet potato to Europe, and by the end of the 15th century it was established in China and the Philippines. China now produces and consumes far more sweet potatoes than the Americas, enough to make it the second most important vegetable worldwide. There are many different varieties, ranging from dry and starchy varieties common in tropical regions, some pale and others red or purple with anthocyanins, to the moist, sweet version, dark orange with beta-carotene, that is popular in the United States and was confusingly named a “yam” in 1930s marketing campaigns (for true yams). The bulk of the U.S. crop is grown in the Southeast and cured for several days at 86°F/30°C to heal damaged skin and encourage sugar development. True to their subtropical heritage, sweet potatoes store best at 55–60°F/ 13–16°C. Chilling injury can contribute to “hardcore,” a condition in which the root center remains hard even when cooked.