The Vegetable Garden

    Potato, Sweet - When To Plant

      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. To grow your own plants, place several sweet potato roots about one inch apart in a hotbed and cover with two inches of sand or light soil. Add another one inch of sand when the shoots begin to appear. Keep the soil in the bed moist throughout the sprouting period, but never allow it to become waterlogged. Keep soil temperature between 70° and 80°F. Plants are ready to pull in about 6 weeks (when they are rooted and 6 to 8 inches tall). You can allow roots to continue possibly producing additional flushes of plants if more are desired. The sprouts (slips) are planted directly in the garden from the sprout bed.

      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.

      Care

      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.

      Harvesting

      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 placed in a warm room for curing (85°F and 85 percent humidity (if possible) for 10 to 14 days and then stored in a cool (55°F) 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.

      Common Problems

      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.