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AUTHOR

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

Sweet Potato: A Thanksgiving Tradition

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

Published: November 16, 2021

sweet potatoes

As the annual ritual known as Thanksgiving dinner draws near, it's interesting to speculate what might have been on the menu at the very first Thanksgiving in 1621. We know from a letter written to a friend by Edward Winslow, an English leader who attended the event, that waterfowl, venison and seafood dominated the meal. Corn also was mentioned in the letter, but everything else that was consumed during the three-day feast is speculation. Most likely it was produce gathered from the wild or grown by the colonists in their gardens. In either case, potatoes of any type would not have been available.

painting of pilgrams and indians

Artist's rendition of first Thanksgiving. (credit: plus.google.com)

Today, Thanksgiving dinner mainstays include turkey, stuffing, mashed potatoes and gravy, cranberry sauce, pumpkin pie and, of course, sweet potatoes. The latter often are disguised as "candied yams," mashed and smoothed under marshmallows in a casserole. Indeed, even those who distain sweet potatoes feel obligated to serve them at Thanksgiving, lest they be accused of breaking with tradition. The origin of the tradition of serving sweet potatoes at Thanksgiving is interesting, if not somewhat mysterious.

Sweet potato (Ipomea batatas) is a member of the Convolvulaceae,or morning glory, plant 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.

freshly dug up sweet potatoes in a field

Freshly dug sweet potatoes.

Columbus quite likely 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 introducing it to Spain around 1500, and a number of different types were cultivated there by the mid-1600s. Sweet potato was very slow to spread to more northern regions of Europe because of it long growing season and need for 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 food staple of the South. Even today, sweet potato is much more popular in the southern states than then northern ones, due in part to the South's more favorable production environment.

The skin color of sweet potato varies fairly extensively among cultivars However, 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 sp.) are perennial herbaceous vines cultivated in tropical regions of the world for their starchy tubers. Today, although available in supermarkets, yams mainly are a curiosity in the United States and not widely consumed.

purple sweet potatoes next to tan sweet potatoes

Examples of variation in sweet potato skin color.

The exact origin of the tradition of including sweet potatoes on the Thanksgiving dinner menu remains uncertain. However, much credit is given to writer, activist, and an influential editor Sarah Josepha Hale who was a staunch advocate for the creation of Thanksgiving as a national holiday. Hale wrote letters to a number of President Lincoln's predecessors including Taylor, Fillmore, Pierce and Buchanan, without success. It was her letter to President Lincoln in 1863 that convinced him to support legislation establishing a national holiday of Thanksgiving.

pie in an oven

A recipe for sweet potato pie published in 1887 is credited with helping to associate sweet potato with Thanksgiving. (credit: Stephanie Clifford)

Later, Hale included a recipe for sweet potato pie in a magazine article she wrote in 1887. The recipe, along with Hale's reputation as the "godmother of Thanksgiving," no doubt, helped to set the stage for the sweet potato tradition. In 1893, Fannie Farmer, author of the Boston Cooking School Cookbook, included a recipe for glazed sweet potatoes in her publication. By early in the 20th century, recipes for candied sweet potatoes were common in the United States and appeared in Martha McCulloch-Williams' 1919 book Dishes from the Old South and the International Jewish Cookbook published by Florence Greenbaum the same year.

As an interesting aside, much of the increased interest in sweet potato at that time can be credited to renowned African-American agricultural scientist George Washington Carver. Born into slavery in Diamond, Missouri, Carver is best known for his work with peanut. However, he also had a keen interest in sweet potato and is credited with developing over 125 diverse products from the vegetable including dyes, wood fillers, candies, pastes, breakfast foods, starches, flours, and molasses.

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 carbohydrates (for energy), it contains essential minerals, dietary fiber, protein, beta carotene (pro vitamin A), vitamin C and vitamin B6. Sweet potato per se is relatively low in calories (a 100 g. serving is reported to contain about 115 calories). However, when caramelized with brown sugan and topped with marshmallows, it becomes much higher in caloric content.

sweet potato casserole with marshmallows on top

Sweet potatoes topped with marshmallows originally was created to promote marshmallow sales. (credit: foodnetwork.com)

The tradition of topping a sweet potato casserole with marshmallows is interesting in and of itself. In 1917, a company called Angelus Marshmallows (the original maker of Cracker Jacks) hired Janet McKenzie Hill, founder of the Boston Cooking School Magazine, to develop recipes featuring marshmallows to promote sales. One of the recipes she concocted included mashed sweet potatoes topped with marshmallows. The rest, as the saying goes, is history.

For readers who would like to grow sweet potato in their gardens next year, it 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.

sweet potate vine with roots

Sweet potato "slips" ready for planting. (credit: agintheclassroom.com)

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 are more productive if provided with about one inch of water per week.

Sweet potato is relatively pest free. Soil borne insects can be a problem if the ground planted to sweet potato was in sod the previous year. Diseases that can infect sweet potato include stem rot, soft (bacterial) rot, black rot, nematodes and scurf (a storage disease). 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 labelled for vegetables.

planter with sweet potato foliage

Ornamental sweet potato 'Illusion Midnight Lace'. (credit: ProvenWinners.com)

Finally, as a species, sweet potato is very prone to form bud sports. The latter are chance mutations which differ from the parent plant. Bud sports with desirable characteristics are often propagated vegetatively to form new cultivars. In the case of sweet potato, the tendency of mutations to form has led to the introduction of a number of new ornamental sweet potatoes with unusual, attractive leaves. Ornamental sweet potatoes are used mainly as annual ground covers or in colorful containers. Although ornamental sweet potatoes produce storage roots which are edible, the table quality leaves much to be desired, in the minds of most who have tried them.


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REVISED: November 19, 2021