Climbing, spilling, sprawling: sweet potato vines can do it all
Sweet potato vines have become a very popular colored foliage plant to use in container gardens, borders and flower beds in recent years. Some of the commonly grown varieties of foliage vines are: Blackie, with deep purple to nearly black foliage; Marguerite, which has bold chartreuse green, heart-shaped leaves; Sweet Caroline, whose hand-shaped leaves are shades of coppery bronze; and Tri-color or Pink Frost, which has green leaves with accents of pink and white. Every year new foliage colors are being developed. Sweet potato vines usually do not have any flowers except Blackie, which sometimes has small lavender flowers.
Ornamental sweet potato vines, Ipomoea batatas, is a true sweet potato complete with tubers, but gives big impact with its bolder colorful foliage than its vegetable sibling. It is grown for it decorative foliage, vigorous growth habit (2 feet tall and spreads to 5 feet) and drought tolerance. While they are sweet potatoes, they are not potatoes, but are in the same family as morning glories, Ipomoea tricolor. One can easily see the similarity in the leaves and the lavender flowers that sometime appear on the Blackie variety.
The unique foliage and forms make ornamental sweet potato vines popular as "spillers" in containers and as "sprawlers" in border flower gardens. If you feed them with a half-strength liquid fertilizer once a week they will reward you with a fantastic display of growth. One sweet potato vine in a container will quickly fill in and around the rim of the pot and spill over its edges. In the garden, sweet potato vine is an impressive, fast-growing annual ground cover that should be planted no closer than two feet apart. It can be easily trimmed when it outgrows its boundary or strays too far from its container. Unlike its cousin, the morning glory which is grown from seed, the cutting you trim off an overgrown sweet potato vine can be planted directly into the soil where you want it, and if the area is kept moist, it will take root and grow.
The sweet potato vine is a tropical plant and grown as an annual. Though full sun is preferred, it will grow in partial shade. Keep the soil moderately moist or the vines will quickly wilt, with limp flagged leaves. Fortunately they are very drought tolerant and will quickly perk up once thoroughly watered. When grown in containers some of the tubers roots have grown so large that they protrude out the top of the pots and in some cases actually bursting pots apart toward the end of the growing season. The new varieties that are being developed have a smaller tuber and are less vigorous, making them more suitable for smaller containers.
The large tuberous roots are edible but most have a poor flavor or even a bitter taste. At the end of the growing season you can dig up the tubers and store them in peat moss so they do not dry out and at a temperatures of about 35 degrees. These same plants (tubers) can be grown again next season. They are very easy to root and can be grown indoors as a houseplant.
To root a tuber in the spring, use a wide mouth container. Insert four toothpicks into the sides of the tuber, about half way up. These toothpicks will support the tuber on the top of the container. Fill the container with enough water to cover the tapered end of the tuber, and set the container in the sun. It usually does not take long for the roots to sprout. In about a week roots should be growing down into the water and shoots beginning to grow up on the top of the potato. The water should be changed each week. In about 4 to 5 weeks the sweet potato vine can be transplanted out in your garden or container, after there is no danger of frost.
Morning glories, Ipomoea violacea, on the other hand are grown from seed and the twining vine will need some type of support as it may grow as much as 20 feet in one season. Before planting it is best to soak the seeds for 24 hours and plant outside after there is no danger of frost. It is important to remember that the soil for morning glories should not be too fertile (nor should you fertilize them) or be too moist as these conditions stimulate the growth of foliage and not flowers. Besides the classic "heavenly blue" morning glories come in shades of pink, purple, red and white, and are favorites of hummingbirds and butterflies. After morning glories freeze down at the end of the season, you may need to use pruning shears to cut the twining vines off the support. Some varieties of morning glories will reseed themselves.
Kyle Schulz is a Wadena County Master Gardener from Sebeka, and the regular gardening columnist for the Wadena Pioneer Journal.