Though few people would dare think of covering up a steak or bowl of fresh steamed broccoli with marshmallows, sweet potatoes are often adulterated in this manner. It’s a pity because people are missing out on the true flavor of one of nature’s most nutritious, naturally sweet vegetables.
Sweet potatoes are a member of the morning glory family, says Jerry Goodspeed, Utah State University horticulturist. Though native to South America, they grow throughout the world — including Utah. Classified as a frosttender perennial, they are grown as an annual in Utah. In addition to their food value, sweet potatoes are also often grown for their ornamental value as a ground cover or trailing vine.
The trick to growing sweet potatoes in Northern Utah is starting with a healthy transplant and growing it in welldrained, fertile soil, Goodspeed says. Plant them after the danger of frost is past in the spring. A transplant, or "slip" as they are called, can be bought at some of our local nurseries, ordered through the mail or started indoors from a tuber.
“To grow a slip indoors, start it about six to eight weeks before you expect to plant it into the garden,” he suggests. “Select a firm, healthy sweet potato. Submerge half the tuber in water by filling a jar with water and sticking tooth picks in the tuber so half of it remains above the top of the jar. It can be placed horizontally or vertically. Be sure to provide it with as much sunlight as possible.
“After a couple of weeks roots will start to develop and leaves will begin to grow. This section is known as the slip. Once three to five leaves develop, it can be moved to a cold frame or planted in a pot in light soil to continue its growth,” he says.
After the danger of frost has passed, move them outdoors to the garden, he says. If they are being grown for their ornamental value, plant them near a fence or trellis.
“They do best when grown in a raised bed,” Goodspeed says. “This is a great environment for the tubers to develop and allows room for the plants to grow. One healthy sweet potato plant can reach a size of four to six feet in diameter or grow up a four-foot fence with little trouble. Serious sweet potato growers cover the raised beds in plastic and plant the slips through cut slits. This helps conserve moisture, reduces weed competition and keeps the soil warm.”
Water the plants deeply and infrequently, he adds. Although they have few pests, they can suffer from root rot in overwatered soils. Growing them in a raised bed helps ensure proper drainage. Fertilize at planting time with an all-purpose fertilizer.
In the fall, dig up the tubers before frost kills the tops, Goodspeed says. Most growing seasons in Utah produce smaller tubers than what is found in the grocery stores. However, some growers have reported large, sweet roots that outdo any sweet potatoes available in our local stores.
There are a number of varieties available through mail order catalogs, though most nurseries offer only one or two varieties, he says. The most commonly grown in the United States is Centennial.
For more information, contact your local USU County Extension office.
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