I think I've seen ornamental sweet potatoes growing in every town I've visited this summer. Just a few short years ago, this was not the case. Why have they become such a popular plant?
One reason is their adaptability. Whether used as ground cover, in a hanging basket, or trained on a trellis, sweet potato will thrive. They are also very heat tolerant, so the heat of a central Illinois summer will not phase them!
Ornamental sweet potatoes are vigorous growers, filling space in a very short time. For people that want their landscape filled in yesterday, this is a very good thing. If you have not anticipated this growth, sweet potato vines may be threatening a hostile takeover of your garden. All is not lost–the vines can be trimmed back. Just remember to allow plenty of room in future plantings.
I've been asked whether ornamental sweet potatoes are the same as those we eat. The answer is yes and no. They are the same species as those sweet potatoes we eat (Ipomoea batatus) but have been selected for their unique foliage rather than tubers. You could eat the tubers from ornamental sweet potatoes, but they are typically white, and they don't taste very good.
The ornamental sweet potato variety 'Blackie' was around for several years but didn't catch on. Dr. Allan Armitage of University of Georgia is credited with bringing attention to ornamental sweet potatoes with his introduction of the lime green variety 'Margarita', which was a chance plant spotted in nature and propagated. Since popularity of the ornamental sweet potato has skyrocketed, so have deliberate breeding efforts to introduce new varieties, often with variegated or otherwise colored foliage.
'Tricolor' is a particularly striking variety with shades of green leaves streaked with white and pink. Typically, sweet potatoes are planted in combination with other plants. Seldom have I seen them as stand alone plantings. One combination that I see often is the bright lime green 'Margarita' with deep purple plants, such as coleus, purple fountain grass, or even another sweet potato, such as the deep purple 'Blackie'.