The sweet potato (Ipomoea batatas) is a starchy, sweet-tasting root vegetable belonging to the morning glory family (Convolvulaceae). It is only distantly related to the common white potato. The edible part is the enlarged storage root, not a stem tuber. Growing sweet potatoes at home offers high yields of a nutritious crop that thrives in warm weather and requires relatively low maintenance once established.
Preparing Sweet Potato Slips
Sweet potatoes are grown from small sprouts called slips, which are essentially rooted stem cuttings, rather than seeds or potato eyes. Starting slips is the first step in cultivation and typically takes about four to six weeks before they are ready to plant.
Slips can be started by suspending a mature sweet potato in water, ensuring the bottom half is submerged, or by placing the potato horizontally in moist sand or a soilless mix. The sand method is often faster and more productive, with sprouts typically emerging after a few weeks. Keep the sprouts in a warm environment, ideally around 75°F to 85°F, to encourage rapid growth.
When sprouts reach five to six inches in length and have developed roots, they are ready to be detached. The slips are carefully twisted or cut from the mother potato. If slips lack roots, place them in a jar of water for a few days to encourage rooting before planting. This vegetative propagation method ensures the resulting plants are true to the parent variety.
Site Selection and Transplanting
Sweet potatoes require full sun for maximum yields, ideally receiving eight to ten hours of direct light daily. The soil must be consistently warm, reaching at least 65°F after the last danger of frost before transplanting. Planting in raised rows or hills is recommended because this practice helps the soil warm up faster, improves drainage, and provides loose soil for the storage roots to expand.
The best soil is a loose, well-drained, sandy loam with a slightly acidic pH between 5.8 and 6.0. Heavy or clay soils can cause misshapen roots or lead to root rot due to poor drainage. Avoid using high-nitrogen fertilizers or manure, as excess nitrogen encourages vine growth at the expense of developing storage roots.
When transplanting, set the slips into the prepared soil with at least two nodes buried for good root establishment. Space the plants approximately 12 to 18 inches apart to allow enough room for the storage roots to develop fully. Immediately after planting, thoroughly water the slips to settle the soil and reduce transplant shock. Consistent moisture is necessary until the plants are established.
Essential Mid-Season Maintenance
Once the sweet potato slips are established, the plants are relatively self-sufficient. Consistent moisture is important for the first 50 to 60 days after transplanting, especially during dry periods, to facilitate tuber initiation. Avoid overwatering, as soggy conditions can cause the roots to split or rot.
The aggressive, trailing vines grow rapidly, effectively shading out most weeds after the first few weeks, minimizing the need for weeding. Pruning the vines can reduce yield, but controlling long runners may be required to prevent them from rooting elsewhere and diverting energy from the storage roots. Minimal fertilization is needed, but a low-nitrogen, high-potassium side-dressing can be applied mid-season if growth appears slow.
Sweet potatoes are subject to a few pests, most notably the sweet potato weevil, which can cause significant damage by boring into the roots. Other pests include wireworms and cucumber beetles. Organic control methods include crop rotation, encouraging natural predators, and using organic insecticides such as neem oil for above-ground pests.
Harvesting and Curing for Storage
Sweet potatoes are ready for harvest approximately 90 to 120 days after transplanting, or when the leaves begin to yellow as the growth slows down. Harvest must occur before the first hard frost, as cold soil temperatures below 50°F damage the roots and negatively affect their storage quality. Cut the vines off at the soil line a few days before digging to make the harvest process simpler.
The roots have delicate, thin skin that is easily bruised or scratched. Use a garden fork or spade to gently loosen the soil far away from the main plant to avoid piercing the roots. Once lifted, brush the roots free of excess soil; do not wash them before the curing process begins.
Curing is a mandatory post-harvest step that converts starches into sugars, which significantly enhances the sweetness and flavor. This process also allows minor skin injuries to heal, forming a protective cork layer that extends storage life and reduces the chance of decay. Ideal curing requires a high temperature of about 85°F and a high relative humidity of 85% to 90% for four to fourteen days.
Home gardeners can achieve curing by placing the roots in a warm, enclosed space, like a sunny window or a covered porch, or by using a makeshift tent with a heater and a source of moisture. After curing, the sweet potatoes should be moved to a cooler storage location, ideally between 55°F and 60°F with high humidity, to prevent sprouting and shriveling. Properly stored sweet potatoes maintain quality for several months.