Daniel Gill, Merrill, Thomas A.
Get It Growing News For 05/18/07
LSU AgCenter Horticulturist
We generally are interested in something to eat when we grow vegetables. In some cases, however, certain vegetable cultivars have been bred and selected for their ornamental characteristics rather than food quality.
To distinguish these vegetables, grown for their looks rather than their eating quality, the word "ornamental" is used with their names, such as ornamental cabbage, ornamental kale and ornamental peppers.
For the summer flower garden, ornamental sweet potatoes (Ipomoea batatas) make a delightful, attractive addition. They love the intense heat of our summers and should not be planted until the daytime highs are in the 80s. May through August is the perfect time to add them to your landscape in Louisiana.
Like their edible relatives, ornamental sweet potatoes are vining plants related to morning glories, but the ornamental types are grown strictly for their attractive foliage. They do produce fleshy tuberous roots like their edible counterparts, but the quality of the roots is really not suitable for eating.
These easily grown plants work well as a low-growing bedding plant, as a ground cover, in hanging baskets and other containers or when trained to climb a support. The growth on these plants is very vigorous once they get established, and they can be used to cover large areas of landscape beds. They also look nice weaving among other flowers or shrubs – if kept under control. But these enthusiastic plants are not the best choice for small beds or detail work, since they will outgrow those situations.
When planted in a bed with other plants, you will need to watch the situation carefully to make sure the ornamental sweet potatoes do not overwhelm the other plants. The best type for this purpose is "Tricolor," since it is less vigorous. Trim as needed to control these enthusiastic plants. If you need more ornamental sweet potato plants, the cuttings will root effortlessly in water or soil.
Ornamental sweet potatoes generally will not flower under normal garden conditions. Although attractive, the small, lavender, trumpet-shaped flowers would not contribute much to the display even if they did. The colorful foliage is the big show, and it is produced until the first frost. At that time these plants go dormant – but it’s important to realize they are dormant, not dead. Once planted, ornamental sweet potatoes generally will return from their perennial roots year after year.
Ornamental sweet potatoes do best and are most colorful in locations that receive full to part sun (about six hours or more of direct sun). They will grow in shadier conditions, but the vines will not be as vigorous, and the color may not be as intense.
Average garden soil, fertility and watering will keep these undemanding plants happily growing all summer.
Although relatively carefree, there are a few problems to watch out for. Pest problems include the sweet potato looper – a caterpillar that chews holes in the leaves – and the sweet potato whitefly. Control the looper with occasional applications of an insecticide containing Bt, spinosad or carbaryl (Sevin). Sweet potato whitefly can be controlled with Year Round Oil (spray under the leaves in early morning when it’s cool), Talstar, malathion or acephate (Orthene). But such problems generally are minimal.
In Louisiana, distribution of ornamental sweet potatoes into portions of the state where sweet potatoes are grown commercially and that have been declared free of sweet potato weevils is regulated by the Louisiana Department of Agriculture and Forestry. This restriction primarily involves parishes located in the northeastern part of the state. Check with your parish LSU AgCenter Extension office for details on whether it affects your area.
Three main cultivars of ornamental sweet potatoes are available. "Blackie" has deep purple leaves with an attractive, unusual shape. The dramatic foliage makes a striking contrast with flowering plants in a variety of color schemes. "Margarita" is known for its lime green or chartreuse, heart-shaped leaves. "Tricolor" (also called "Pink Frost") is a striking multi-colored cultivar with light green, pink and white foliage. It is much less vigorous than "Blackie" and "Margarita" – making it easier to control and more useful in mixed beds.
Two other cultivars that are available are "Black Beauty" and "Ace of Spades." Both have deep purple leaves similar to "Blackie," but the leaves are heart shaped.
The Sweet Caroline series of ornamental sweet potatoes was selected at the J.C. Raulston Arboretum in North Carolina and released a few of years ago. There are four colors in the series: green, bright lime green, purple and bronze. All of the colors have deeply lobed leaves similar to "Blackie." The most exciting and unique color is the "Sweet Caroline Bronze," which has foliage that is an indescribable coppery-bronze on top and violet underneath.
The landscape performance of these and other cultivars is being evaluated by the LSU AgCenter at the Burden Center in Baton Rouge.
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at www.lsuagcenter.com. A wide range of publications and a variety of other resources are available.