Sweet potato, Ipomoea batatas, is a tender, warm weather vegetable that requires a long frost free growing season to mature large, useful roots.
Sweet potatoes, which are related to the morning glory, grow on trailing vines that quickly cover the soil, rooting at the nodes along the way. “Bush” varieties with shorter vines are available for situations where space may be limited.
For their ornamental value, sweet potatoes are often grown as ground cover or in hanging baskets, in planters and even in bottles of water in the kitchen. Cut-leaf types exist that are particularly attractive. The sweet potato is rich in vitamin A. It is not related to the yam, though in the marketplace the two names are often used interchangeably. The true yam, Dioscorea sp., is an entirely separate species that grows only in the tropics.
Beauregard (100 days to harvest, light purple skin, dark orange flesh, extremely high yielder.)
Bush Porto Rico (110 days, compact vines, copper skin, orange flesh, heavy yield.)
Regular Porto Rico (yam family, orange, nice size, thick potato. Moist with a very sweet and delicious flavor. Excellent for baking.)
Gold Mar (high yield of uniform shape and size, deep orange-moist potato)
Jewell (100 days, orange flesh, good yield, excellent keeper.)
Vardaman (110 days, golden skin, orange flesh, compact bush type, young foliage purple.)
Yellow Jersey (golden yellow skin, flesh color ranges from creamy white to bright yellow with an occasional pink variegation.)
When To Plant:
Sweet potatoes are started from plants called “slips”. Transplant the slips as soon as the soil warms up after the last frost to allow the maximal warm weather growing period. Always buy plants grown from certified disease-free roots.
Spacing & Depth:
Set the plants 12 to 18 inches apart, preferably on a wide, raised ridge about 8 inches high. A ridge not only dries better in the spring but also warms earlier than an unridged area. Black plastic mulch can be a good way to speed early season growth by capturing and storing more of the sun’s heat in the soil under the plastic cover. Because the vines of spreading varieties need a great deal of space, allow at least 3 to 4 feet between rows.
After early cultivation (which is not necessary with black plastic), sweet potatoes need minimal care to keep down weeds. Once the vines spread to cover the ground, little weeding is required. Irrigate if an extended drought occurs. Do not water during the last 3 to 4 weeks before harvest to protect the developing roots.
Early roots may be “robbed,” starting in late summer, by digging into the side of the ridge and carefully removing some developing roots while leaving the plant in place. Dig the main crop of sweet potatoes around the time of the first frost in the fall. Use a spading fork or stout shovel and be careful not to bruise, cut or otherwise damage the roots. Dig below the level of the ridge and gradually move closer toward the plants, removing soil until the fat roots are exposed. Carefully dig under these roots to gauge the depth to dig as you go down the row.
Proper curing can be a problem in the cool fall season. Ideally, the roots should be allowed to dry on the ground for 2 to 3 hours, then place in a warm room for curing (85 degrees and 85 percent humidity (if possible) for 10 to 14 days and then stored in a cool 55 degree location. Sweet potatoes should be handled as little as possible to avoid scuffing and bruising. In case of frost, cut the vines from the roots immediately to prevent decay spreading from the vines to the roots and dig sweet potatoes as soon as possible. Cold soil temperatures quickly lessen the roots’ ability to keep in storage. Do not allow roots drying in the garden to be frosted because they are quickly ruined. For best quality, use the potatoes as soon as possible after they have been stored.
To prevent diseases, plant varieties with multiple resistance, use “certified” plants and rotate sweet potatoes’ location in the garden. At certain sites, mice may become a problem by burrowing into the mound and eating the tasty, nutritious roots before harvest can commence. Check for evidence of mouse infestation regularly and apply appropriate control measures as needed.