The holidays mean it is sweet potato season. Whether you cook them in sugary syrup (my mother’s “candied yams”), whip them with eggs and sugar into a casserole topped with pecans or marshmallows, or bake, peel and eat them unadorned, sweet potatoes are tasty. They also pack a powerful dose of vitamins, minerals and fiber. In colonial times they were commonly used as an addition to livestock foods. Think Scarlett O’Hara biting into a raw one to soothe her gnawing hunger. And while you are considering sweet potato history, recall that Popeye said, “I yam what I yam” all the way back in 1933.
Native to the Americas, these relatives of the morning glory grow well in the long, hot summers of the deep south. As a gardener, I will never complain about too much rain, but the past summer was so moist that many sweet potatoes at local farms rotted before they could be harvested. The tubers grow underground and should be lifted and allowed to dry in the shade a few days before being stored. This drying helps heal small wounds created in the digging process and converts some of their starch to sugar. Properly cured, they will last for months if kept 50 to 60 degrees and low humidity. Do not store in the refrigerator. Do not wash before storing.
Sweet potatoes are started from slips, or sprouts that originate from the skin of a mature tuber. You can grow your own slips, but I always purchase them to ensure a disease-free start. The soil should be warm before the slips go into the ground – 65 degrees or better. In upstate SC, this can mean early to middle May. Once planted, they require little in the way of maintenance beyond a bit of weeding and the occasional irrigation in dry periods. Be careful not to damage the shallow roots when cultivating.
We have grown the varieties ‘Beauregard’ and ‘Centennial’ in the Mary Snoddy garden. The last planting of Beauregard yielded such a heavy crop that we ate them almost every day, until their deliciousness became tiresome.
The first time I grew them, I underestimated the vines’ space requirements. Now I know to plant the slips about 18 inches apart and to allow three feet between rows. I also learned that when the natural soil is heavy clay, the prettiest sweet potatoes are grown in raised rows. This does not have to be a complicated process. Just dig two shallow trenches on either side of your planned planting line. A square shovel works great. Throw the excavated soil atop the row, level lightly with a rake, and plant on top of the flattened ridge. The loose soil nurtures large, smooth roots. When not grown on raised rows, the roots can become contorted in heavy or rocky soil. The plants will still produce a harvest but the potatoes will be smaller and more difficult to peel.
While the terms are sometimes used interchangeably, yams are drier and lighter in color than sweet potatoes. True yams are rarely seen in American grocery stores.
Sweet potatoes leaves are sometimes attacked by Japanese Beetles, but the vines are so vigorous that the damage does not extend to the potatoes. Deer find the foliage extra-tasty, so when their populations are high the gardener may need to use floating row covers or other means to protect the vines.