This is the week a treasured favorite graces many Thanksgiving tables: baked candied yams and marshmallow. As a child I never questioned this, as the flavors of “candied yams” and marshmallows seemed so perfect together, and I was raised in Northern Michigan where I didn't know much about yams.
My first job after college was working at a vegetable crop research station in the Caribbean and I was quite shocked to learn that “candied yams” are not yams at all, but orange-fleshed sweet potatoes; yams are a completely unrelated species. The USDA requires that all cans labeled yams also list sweet potato, but confusion still exists.
Sweet potatoes (Ipomoea batatas) are from the Convolvulaceae family, also known as the morning glory family. Other plants in this family include morning glory vine, water spinach and bindweed. Botanically, sweet potatoes are enlarged roots and yams (Dioscorea alata) are stem tubers, but the skin of yams is very tough and brown, the flesh is usually starchy and not sweet, and the tubers can be very large. Yams can only grow in a tropical area, or in a heated greenhouse.
High in vitamins A and D and fiber, sweet potatoes are vegetatively propagated and not grown from seed. Backyard growers either produce their own “slips" or transplants by putting the root end in water, sprouting and then breaking off the eyes; or purchasing slips from a commercial production company or garden center.
Sweet potato can have many different colors of flesh and skin. The type the U.S. population is most familiar with are orange-fleshed varieties that tend to be moister than the white- or cream-fleshed types grown throughout the world, and there are even blue-fleshed varieties. In some cultures, the foliage is consumed as a fresh green.
Sweet potatoes have a long, storied history in the United States. The center of origin is thought to be Central and South America, and tubers were brought to the Old World by Columbus. The crop was moved to the Pacific Islands and parts of Asia much earlier.
Due to the ability to easily store the mature tubers and their high caloric content, sweet potatoes were a very important food crop for the early colonists and settlers, particularly during the Revolutionary and Civil War and the Great Depression. Sweet potatoes were a staple in the Southern colonies and were fed to enslaved persons, who called sweet potatoes “nyami,” a word for the true yam common in Africa. Over time, many markets commonly referred to sweet potatoes as yams and thus, sweet potatoes became known as yams.
The famous scholar and inventor George Washington Carver developed over a hundred products from sweet potato, such as glue, and suggested the use of sweet potato as a rotation crop for cotton.
The top-producing sweet potato state is North Carolina with 95,000 acres harvested in 2016. Others are California, Mississippi and Louisiana. Production in Ohio is growing but limited to small farms and backyards. According to a recent Ohio State University VegNet Newsletter, one farmer in Athens County produced a 14-pound tuber! To learn more about this see u.osu.edu/vegnetnews/2018/11/09/farmer-focus-vest-berries.
The most widely grown variety for the home market is ‘Beauregard,’ but others such as ‘Covington’ and ‘Centennial' also do well in the region. If growing your own, use plant slips that are at least 6 inches long and plant after the last frost, about a foot apart. Sweet potatoes do not tolerate cold weather and should be planted in a loose soil bed. Weed shallowly until the foliage fills in. Hill the plants as the season goes by and harvest before a killing frost.
If not consuming right away, sweet potatoes need to be cured by holding at a temperature of 80 to 85 degrees and high humidity for several days. The tubers should be stored in a cool, but not freezing location and should last several months.
Wishing all a bountiful Thanksgiving.
For more information about sweet potato, see canr.msu.edu/resources/how_to_grow_sweet_potatoes.
Jacqueline Kowalski is the Summit County Agriculture and Natural Resources Extension Educator for the Ohio State University. For questions on local foods, food production or other garden-related questions, contact her at firstname.lastname@example.org or 330-928-4769, ext. 2456.