Sweet potato (Ipomoea batatas) is a trailing vine in the morning glory family grown for its starchy, sweet tuberous roots. It is only distantly related to the common potato and is not a true yam, despite the terms being used interchangeably in North American markets. Young shoots and leaves are also edible and are used as cooked greens in Asian and African cuisines. The plant is a staple crop across tropical and subtropical regions and is one of the most productive calorie crops per acre in warm climates.
Sweet potato requires a frost-free growing season of 90–120 days and warm soil. It is propagated from slips — rooted shoots sprouted from stored tubers — rather than direct seed. Loose, slightly acidic, well-drained soil encourages large, well-formed tubers; heavy clay causes misshapen roots and rot. In zones 9 and warmer it can persist as a perennial. In cooler zones it is grown as an annual. Tubers must be cured at 85–90°F with high humidity for 7–10 days after harvest to heal skin wounds and convert starches to sugars, which significantly extends storage life. Vines root at nodes along the ground; redirecting or lifting them prevents adventitious roots from competing with the main tuber crop.
Orange-fleshed cultivars are among the richest dietary sources of beta-carotene. The root is also high in vitamin C, potassium, and fiber and has a lower glycemic index than white potato despite its sweetness. Leaf extracts have been studied for anti-inflammatory and antihyperglycemic activity. Purple-fleshed cultivars contain anthocyanins with documented antioxidant properties.
Root-Knot Nematode
Swollen galls on roots, poor vigor, wilting in heat, and reduced fruiting. Containers and sandy soils are more prone.
Use clean potting mix in containers. Avoid replanting in infested soil. Maintain plant vigor with mulch and steady watering. Solarize affected garden soil.
Fusarium wilt
Sudden wilting, brown streaks in stems, yellowing leaves. Affects sweet basil varieties most.
No cure. Remove and destroy plants. Do not replant in the same spot for 3+ years. Choose resistant varieties.
Bacterial Soft Rot
Rhizomes turn mushy and foul-smelling; foliage yellows and pulls away easily at the base. Often follows borer damage or overly wet soil.
Cut away all soft tissue back to firm rhizome, let it dry, and dust the cut with sulfur. Improve drainage and avoid burying rhizomes. Destroy badly infected plants.
Sweet Potato Black Rot
Dark brown to black, circular, sunken lesions on tubers. Infected flesh is bitter and inedible. Lesions may expand in storage and produce olive-green spore masses.
Use only certified disease-free slips. Cure tubers promptly and thoroughly before storage. Discard any infected tubers immediately. Rotate to non-host crops for at least 3 years.
Sweet Potato Scurf
Brown to black, irregular superficial discoloration on tuber skin giving a sooty or dirty appearance. Does not penetrate flesh but reduces quality and can shorten storage life.
Plant certified clean slips. Avoid replanting in infested soil for 2–3 years. Harvest promptly and cure properly. Store only blemish-free tubers.
Sweet Potato Weevil
Cylas formicarius →Small puncture holes and tunneling in stems, roots, and tubers. Infested tubers emit a sharp, bitter odor and the flesh may turn dark. Adults are ant-like with a blue-black body and reddish-orange legs.
Source only certified slip material. Harvest promptly before first frost. Destroy all crop debris after harvest. Rotate to non-host crops for 2+ years in heavily infested sites. Do not plant near other Ipomoea species.