Cut open one of the sweetest sweet potato varieties and you'll find white flesh, not orange.
Most grown commercially in the U.S. yield tubers with orange flesh and high levels of carotene. Orange-fleshed varieties don't provide the sweetest flavor. Older varieties with yellow or produce more sugar, but won't match the yields or vitamin content of popular orange types. Most white varieties grow best in the Deep South and may be hard to find in other areas.
Sweet Potato Types
Different varieties within the same species produce the two main types of sweet potatoes, with either dry or moist flesh. These terms refer to the texture of the potato and not to the actual moisture content. All sweet potatoes convert some starch to sugar during storage. Orange or moist-fleshed sweet potatoes produce more sugar from stored starch during cooking. Not all white varieties contain high amounts of sugar.
American Varieties
Orange sweet potatoes first became popular in the U.S. in the 1900s because of high yields and extra nutritional value. Worldwide, most sweet potato varieties yield tubers with yellow or white flesh. Regional preferences favor different levels of sugar content. White popular in South America contain higher starch levels, but white and yellow varieties from the southern U.S. yield tubers sweeter than the orange strains. Look for O'Henry for a sugary white American sweet potato with a bushy growth habit; and try Nancy Hall for a yellow-fleshed sweeter heirloom variety. Both O'Henry and Frazier White require only three months to produce crops, but Nancy Hall needs a longer 120 days of warm growing weather. Southern Queen, another long-season white sweet potato with high sugar content, needs 110 days.
Asian Varieties
Purple-skinned Korean sweet potatoes, also well known for their sweeter flavor, yield the typical white flesh of the drier or firmer sweet potato types. This variety requires only 90 days to mature a crop. Don't confuse the Korean Purple Sweet Potato with the Hawaiian Purple Sweet Potato if you're looking for the sweetest flavor. The Hawaiian sweet potato with purple skin and purple flesh originated in Okinawa and has the moist flesh of the familiar orange varieties.
Environment
Sweet potatoes of any variety need storage time to develop their full flavor. After digging, the potatoes convert some stored starch to sugar. Eaten as new potatoes straight from the garden the roots taste less sweet. Store sweet potatoes in a humid space with temperatures between 80 to 85 degrees Fahrenheit for six to 10 days before cooking, suggests Andy's Garden. Maturation times also play a part in sugar content. Growing a long-season variety in a short-season climate won't allow roots to mature to full size or to full flavor.
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