The ornamental sweet potato vine Ipomoea batatas is an annual grown from tuberous roots similar to the green-leaved sweet potato but not meant for producing food. The vine is quick-growing and has lobed leaves. The vine flowers late in summer with a tubular purple flower similar to the morning glory. The flowers are not very noticeable because the leaves are so striking, making the vine more attractive for its foliage.
There are three types of sweet potato annual: Blackie, Margarita and Tricolor. Annuals are plants that bloom throughout the summer season but will not come back from the root the following year. These summer sweet potato vines are grown for their beautiful leaf color. Blackie has dark purple leaves. The Margarita has leaves that are a color between yellow and green known as chartreuse. The Tricolor vine has pale green leaves with white or pink edges.
Sweet potato vines are hardy, or can withstand temperatures, in U.S. Department of Agriculture (USDA) zones 9-11, where average low temperatures do not fall below 25 degrees. Everywhere else they are grown as a summer annual. In cold zones, new plants must be purchased every spring or the vine's tubers must be dug up and stored for the winter until the next spring. If left in the ground, the tubers will freeze. In the plant's hardy zones, tubers can be left in the ground and dug up for dividing to create many plants from one previous plant.
Sweet potato vines do best in full western sunlight. They prefer to be kept in moist, well-drained soil with watering only as needed. Drooping leaves are an indication that the plant needs water. In very hot weather, the plant must be watered regularly. Because the vines grow quickly, they may need to be cut back to control their size. New growth will start to develop immediately where the cuts were made. The plant requires fertilizing with a 15-16-17 mixture. The numbers on fertilizers represent the amounts of nitrogen, phosphorus and potassium plants need for nutrients.
The annual sweet potato vine can be grown as a ground cover. Blackie and Margarita complement each other and can be planted side by side on banks or other visible places. Sweet potato vines also make excellent container plants. They cascade down beautifully from hanging baskets and window boxes. The dark leaves are a great contrast for other plants.
If cared for properly, the sweet potato vine is usually pest free. However, occasionally they can attract slugs if plants are kept in shady, somewhat damp areas of the garden. This is noticeable by the neat-edged holes in the leaves. Slugs can be controlled with slug traps or by putting out shallow plates filled with beer. Slugs are attracted to the yeast smell and will get stuck on the plates.