Go to any garden store in early spring, and you may find a large selection of trailing green or purple decorative vines that are labeled "sweet potato" vines. These decorative vines are actually the top growth for the edible root known as the sweet potato. The sweet potato is not a true potato, and although it is sold in grocery stores as a yam, it is not really a true yam either. There are hundreds of varieties of sweet potato, and each variety is propagated by stem cuttings.
Take cuttings of sweet potato plants in fall before the first frost. To do this, snip off the last 4 to 6 inches of a sweet potato stem near the point where a leaf emerges.
Strip the leaves off the lowest 3 inches of the cuttings.
Place cuttings in a clean, quart glass jar. Fill with water so that the lowest 3 inches are covered with water. Within a few days, roots will form from the points where the leaves emerged.
Watch the potato vine cuttings throughout the winter and refill water whenever it appears low.
Wait until all danger of frost has passed to plant cuttings in spring.
Plant cuttings in the ground to a depth of 3 inches so that roots are completely covered. Water well.