Ornamental sweet potatoes work nicely in mixed containers and as a ground cover, and they have become very popular in the last few years. They are technically perennials, but they are treated like an annual because they are not cold-hardy and the foliage will die after the first freeze.
These versatile plants are often used as drought-tolerant foliage ornamentals for annual flowerbeds and even containers. About this time of year, I often hear from gardeners who want to know if they are true sweet potatoes and are they edible. The large tuberous roots are edible, but most ornamental cultivars have a poor starchy flavor or even a bitter taste. Another consideration is the pesticides that may have been used on them by you or the greenhouse grower. Some insecticides that may be used on nonedibles cannot be used on crops you plan to eat. The bottom line is: we do not recommend you eat them.
To avoid wasting the tubers, you may save them to grow new plants for next year. Prepare the tubers for winter storage by storing them for two or three weeks in a high-humidity, warm environment such as a laundry room. After a few weeks, move the tubers to a cooler area such as an unheated room in your home or the basement. You may want to wrap them individually in newspaper to avoid any rot spreading from one sweet potato to another.
In late winter or early spring, plant the tubers in very well-drained soil with the tubers near the surface. Keep moist, but not overly wet. After a few weeks, the tuber should sprout. When the plants reach 10-12 inches, you may pull them free from the tuber and plant them in small pots or if it is warm enough outside plant them directly in your flower beds or containers. One large tuber may make up to a dozen new plants. These plants are clones; they should be identical to the parent plants.
They are also very easy to root from cuttings and can be grown indoors as a houseplant and used as propagation stock plants for next spring. One consideration when growing them in containers is that there have been some reports of the large roots protruding out of the top of the pots and, in some cases, actually bursting pots apart toward the end of the growing season.
There are several ornamental cultivars available. Margarita (chartreuse color) and Blackie have been around for many years, and the main issue has been their tendency to be overly vigorous. If you are planting in the ground, the extreme vigor may not be an issue or even desired. More recently, the plant breeders are coming up with cultivars that are more compact. You might want to try some from the series called “Sweet Caroline” that has at least five different colors.
They work better in small- to medium-sized planters. Another more recent series is called “Illusion” and has three interesting selections with very beautiful lacy foliage. Both of these series are from the plant company Proven Winners, and should be readily available in garden centers that sell this company’s plants.