The sweet potato vine (Ipomoea batatas) does not generally return every year in temperate or colder climates. Although botanically classified as a tender perennial, it originated in tropical regions of Central and South America. Consequently, it lacks the cold-hardiness necessary to survive winter temperatures typical of most gardening zones. Gardeners outside of continuously warm regions treat the sweet potato as a summer annual, replanting it each spring.
The Annual vs. Perennial Distinction
The plant’s survival is determined by its extreme sensitivity to cold, particularly the ground temperature. Ipomoea batatas thrives in heat, growing best when temperatures are between 65°F and 95°F. A light frost destroys the plant’s leaves and vines, and the tuberous roots suffer damage if the soil temperature drops consistently below 55°F.
Soil temperatures below 55°F cause chilling injury, which can manifest as dark, sunken areas on the tuber surface or a disorder called ‘hardcore’. Due to this sensitivity, the plant cannot overwinter outdoors across the majority of North America and Europe. Only gardeners in U.S. Department of Agriculture (USDA) Hardiness Zones 9 through 11, where temperatures rarely fall below freezing, can expect the plant to return naturally the following spring.
Saving Tubers for Next Season
Gardeners can overcome the sweet potato’s cold intolerance by harvesting and storing the tubers indoors. This process begins by digging up the tubers before a hard frost and initiating a two-step post-harvest treatment. The first step is curing, which heals wounds sustained during harvest, thickens the skin, and converts starches into sugars for improved flavor and storage life.
Curing requires placing the tubers in a warm environment, ideally 80°F to 85°F, with high humidity (85% to 95%), for four to ten days. This heat and moisture encourages the formation of a protective cork layer, preventing decay during long-term storage. Once cured, the tubers must be moved to a cooler, dark location for the winter, maintaining a steady temperature between 55°F and 60°F.
This storage temperature range prevents chilling injury but inhibits premature sprouting, which can lead to dehydration. In late winter, the stored tubers are used to grow “slips,” which are the new sprouts or vine cuttings for the next season’s plants. This method allows the gardener to propagate their favorite variety year after year without relying on the plant surviving the cold soil.
Confusion with Other Ipomoea Varieties
The confusion regarding the sweet potato vine’s perennial nature often stems from its membership in the large Ipomoea genus, which also includes common morning glory species. Many related vines, such as certain ornamental morning glories, are more resilient, either possessing greater cold tolerance or aggressively self-seeding, which gives the illusion of returning each year. The edible sweet potato, Ipomoea batatas, is distinct from these relatives, though it shares the same genus.
Ornamental Varieties
Further complicating the matter is the existence of ornamental sweet potato varieties, which are cultivars of the same species, Ipomoea batatas, but are bred for colorful foliage rather than root production. These ornamental vines are sometimes slightly more tolerant of varying conditions but are still generally grown as annuals in cooler zones. While the tubers of ornamental varieties are technically edible, they lack the desirable flavor and texture of those bred specifically for consumption. Gardeners who notice these ornamental types surviving mild winters are experiencing an exception, not the rule, for the species as a whole.