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AUTHOR

David Trinklein
University of Missouri
Division of Plant Sciences
(573) 882-9631
trinkleind@missouri.edu

Sweet Potato: A Brief History

David Trinklein
University of Missouri
(573) 882-9631
trinkleind@missouri.edu

Published: November 1, 2009

“You say potato, I say patahto” is a familiar phrase to most of us. In either case the word conjures up in the minds of most Americans images of Irish, or white, potato (Solanum tuberosum). However this very common word in the English language was first used to designate sweet potato, an entirely different root vegetable. November brings with it Thanksgiving and an annual feast which usually includes sweet potatoes as well as other horticultural delights. Accordingly, it is an opportune time to learn a bit more about this important food source which (arguably) does not get the respect or use it deserves.

Sweet potato (Ipomea batatas) is a member of the Convolvulaceae, or morning glory, family. The latter contains about 60 genera and over 1600 species, most of which are herbaceous vines. Sweet potato is thought to be native to tropical South America where it has been used as a food source for more than 5000 years.

The natives called the plant batatas. This word eventually became patata in Spanish, patae in French and potato in English. Since the introduction of sweet potato into Europe is thought to have preceded that of Irish potato (another native of South America), the word “potato” was originally a reference to sweet potato and not Irish potato, as is the case today.

Sweet potato probably first migrated from South America in a westerly direction given the fact it has been carbon-dated in the Cook Islands to 1000 A.D. and was grown in Polynesia before the Age of Discovery. Early Polynesians who traveled to South America and back are credited with its introduction to their homeland as well as to Hawaii and New Zealand.

Columbus undoubted encountered sweet potato in his early voyages to the West Indies but it was not until his fourth voyage (to Yucatan and Honduras) that he recorded its discovery in his journals. He is credited with its introduction to the New World (Spain) in about 1500 and a number of different types were cultivated there by the mid-1600s. It was very slow to spread to more northern regions of Europe because of its affinity to warm temperatures.

Sweet potato was grown in what is now Virginia as early as 1648. From there it was taken both north and south. The southern migration of the plant was much more successful than the northern, again, because of the plant’s need for warm temperatures. Native Americans were known to have grown sweet potato extensively by the 1700s and soon thereafter it became a popular staple of the South. Even today, sweet potato is much more popular in the south than the north as a food.

Although sweet potato skin color varies fairly extensively among cultivars, flesh color is either white or dark orange. The white-fleshed types usually are drier in consistency and originally were favored in northern areas of our country. Orange-fleshed types, favored in the South, typically have moist flesh and often (erroneously) are referred to as “yams”. Yams (Dioscorea species) are perennial herbaceous vines cultivated in tropical regions of the world for their starchy tubers. Yams are still mainly a curiosity in the United States.

Sweet potato is a warm-season vegetable that should not be planted until all danger of frost has passed and the soil has warmed. It prefers a well-drained loam soil slightly acidic in nature. Sweet potatoes are started in the garden as vegetative “slips” which can be obtained at many yard and garden stores during the spring or produced by burying storage roots in moist sand and keeping them in a warm location until slips appear.

Space slips 9 to 18 inches apart in rows spaced 36 to 48 inches apart in the garden. Adequate soil moisture and fertility (based on soil tests) should be present before slips are planted. If the soil has been fertilized according to test recommendations before planting, the only additional fertilizer warranted is a light side dressing of nitrogen (12 oz. per 1000 square feet) applied about three weeks after planting and again when the vines begin to “run”. While considered to be drought-tolerant, sweet potatoes bear more heavily if provided with about one inch of water per week.

Sweet potatoes are relatively pest free. Soil borne insects can be a problem if the ground planted in sweet potatoes was in sod the previous year. Diseases that can infect sweet potato include scurf (a storage disease), stem rot, soft (bacterial) rot, black rot and nematodes. Well- drained soil along with good sanitation can help to curtail disease incidence. Weed control is important and can be accomplished mechanically, with mulch or through the use of herbicides.

Most sweet potato cultivars require 95 to 120 days between planting and harvest. One “hill” should yield about two pounds of sweet potatoes given good production conditions.

Pulling the vines several days before digging the roots will help to toughen them and lessen the incidence of skinning. Following harvest, sweet potatoes should be cured in a warm (85 degrees F) and humid (90 percent) environment for several days. This practice produces higher sugar content and better color in the flesh while allowing damaged tissue to heal. Sound sweet potatoes have a storage life from between six to ten months when stored at temperatures of between 55 and 65 degrees F in a humid environment.

Sweet potato is a nutritious vegetable that probably deserves more attention than it gets in the diet of the average American. In addition to being rich in starches (for energy), it contains complex carbohydrates, dietary fiber, protein, beta carotene (pro vitamin A), vitamin C and vitamin B6. Sweet potato is relatively low in calories (a 100 gram serving is reported to contain about 115 calories) and also is an important source of minerals such as calcium, magnesium and potassium.

As an interesting aside, sweet potato has been the subject of a considerable amount of developmental research over the years. African-American agricultural scientist and Missouri native George Washington Carver (best known for his work with peanut) also worked with sweet potato. From the latter he is credited with developing over 125 diverse products including dyes, wood fillers, candies, pastes, breakfast foods, starches, flours, and molasses.

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REVISED: July 10, 2015