Nutritious sweet potatoes and yams thrive in warmer environments. With a few adjustments, you can also grow sweet potatoes in colder climates. Like its relative, the morning glory, the sweet potato is a creeping vine. A white-fleshed variety is still grown in the Deep South, though most commercial potatoes are orange in colour. With less disease and care requirements, sweet potatoes can easily be grown in large numbers or at home in a container using a single vine.
Prepare a site with loose soil that has a pH of 5.0 to 6.5 and full sun. Dry climates work best for sweet potatoes. If growing outdoors, anticipate a spring planting, roughly four weeks after the last frost, and a growing season of up to 150 days.
If sprouting your own plants, submerge one-third of a sweet potato in water. When sprouts are 6 inches long, remove and place in sand or a "hot bed" of loose soil to root. Keep moist and ensure a soil temperature of 21.1 to 26.7 degrees Celsius. Tubers should be fully rooted and ready for planting in six weeks.
Apply a nitrogen fertiliser or compost to soil two weeks before planting. Remove any rocks or other obstacles that might impede tuber growth.
Plant tubers 12 to 18 inches apart on mounded planting rows approximately 8 inches high and 3 feet apart. If growing in a container, insert stake or trellis into loose soil and plant sprout alongside. In both cases, tubers should be loosely covered with soil and kept moist.
Weed periodically. Abundant surface weeds will prevent light from getting to the vines and impede growth.
Irrigate during drought. Keep vines moist but do not overwater and ensure good drainage (sweet potatoes are highly susceptible to root rot).
Do not water sweet potatoes during the last three to four weeks before harvest.
Carefully remove vines and allow them to dry on the ground for two to three hours. Move sweet potatoes indoors as quickly as possible if frost seems imminent.
Cure sweet potatoes in a warm room (approximately 29.4 degrees Celsius) for 12 to 14 days before consumption. Then keep sweet potatoes at 55F for optimal storage.
Plant 1-foot-long cuttings from existing tubers directly into soil instead of sprouts. Spread dark mulch over mounds to retain extra heat and speed early growth. Sweet potatoes make good companion crops for other root vegetables like beets and parsnips.
Do not over water sweet potatoes. Sweet potato weevils and wireworms can attack vines in southern regions. This is not a problem in the North, though mice have been known to burrow into mounds and attack potato roots.