While they are a true sweet potato, they are grown for their attractive foliage rather than their production ability. While they can produce a tuberous root that is edible, it is not highly rated, and rarely eaten. From the dark purple Blackie variety to the chartreuse leafed variety Margarete and a newer variegated foliage plant called Tricolor , these vines rarely, if ever flower, but they produce copious amounts of leaves which can spread up to 12 feet or more. These ornamental types were discovered in the Philippines in the early 1980's. And lest you think all annual vines are morning glories, there are some other highly prized plants.
Hyacinth bean is an old-fashioned vine, making a big comeback.
Hyacinth bean, Dolichos lablab , is a fast growing member of the pea family with large purplish tinted leaves with dark purple stems. These long lasting blooms, are then transformed into glossy purple four inch seedpods, which are every bit as pretty as the blooms. It will grow up to 15 feet in a season. Uncooked beans and flowers are poisonous. Full sun to partial shade.