The sweet potato vine (Ipomoea batatas) is both a widely cultivated root crop and an attractive, ground-covering garden plant that is native to Central America. The food crop varieties produce attractive green foliage, twining stems and and a handsome yield of tubers. There are also a number of varieties with variegated, purple and red leaves which also produce edible tubers but without the flavor of the dedicated crop cultivars. The tubular flowers are purple, but sweet potato vines very rarely set seed.
Plant your sweet potato tubers in rich, free-draining soil in a sunny, flat spot after the last frosts. The tubers will rot if allowed to get waterlogged and shade will limit growth and tuber production. Bury the tubers 2 inches under the surface, allowing 1 square yard of surface per plant. Pinch out the growing tips of new shoots once they are 3 feet long to encourage branching and leaf production.
Water your sweet potato plant when the surface of the soil has completely dried out. Fertilize your vines with nitrogen-rich, liquid fertilizer every two weeks to encourage abundant foliage at the expense of tuber production. The vines will drop leaves if allowed to dry out too much, but the fleshy tuber gives them some resistance to drought. Remove weeds from around your sweet potato vine to keep them in the sun and prevent competition for nutrients. The vines are resistant to most pests but may be eaten by leaf beetles. Treat your vine with an insecticide spray if you notice leaf damage.
Grow showy cultivars such as the purple-leaved Ipomoea batatas blackie and I. batatas tricolor, with green and white leaves with pink margins, together for maximum impact. Sweet potato vines will cascade over a wall and grow well in bright shade under fruit trees. Individual tubers grown in large containers make good patio plants.
Harvest your sweet potato crop at the end of the growing season and raise tubers for storage before the first frosts. In frost-free areas, USDA Zones 9 and above, you can overwinter the tubers in the ground, provided the soil does not get waterlogged for long periods. Store tubers throughout the winter in a cool, dry area. Propagate your sweet potato plant by cutting tubers into several sections, each with a growing sprout or eye. Allow the cut tubers to dry for at least three days before planting, to prevent fungal attack and rot.