Why Are My Sweet Potato Leaves Curling and Distorting?

Sweet potato leaves that curl inward, twist, pucker or develop an irregular, crinkled texture are showing signs of stress — physical, biological or viral. Because sweet potato normally produces large, healthy flat leaves that lie open to maximise light capture, any persistent curling or distortion is a signal worth investigating promptly. Catching the cause early makes management easier and can prevent a minor problem from becoming a major one.

Aphid infestation

Aphids feeding on growing tips and young leaves inject saliva as they feed, which causes the leaf tissue to curl inward and pucker around the feeding sites. The growing tip becomes tightly bunched and distorted, and new leaves emerge crinkled. Check under leaves and at growing tips for clusters of small soft-bodied insects. Treat with a strong water jet to dislodge them, or apply insecticidal soap spray to the undersides of leaves every five to seven days until populations are controlled.

Drought and heat stress

In very hot, dry conditions, sweet potato leaves roll inward along their length (like a cylinder) as a protective response to reduce water loss. This midday rolling usually unfurls in the evening when temperatures drop. If leaves are rolled in the morning before temperatures rise, the plant is genuinely water-stressed. Water deeply and apply mulch around the base to retain soil moisture. This type of curling is uniform — whole leaves roll, not just parts — and there are no pests or distortion of leaf shape.

Virus infection

Sweet potato viruses (including Feathery Mottle Virus and Sweet Potato Leaf Curl Virus) cause persistent, irregular distortion of leaves — particularly the growing tips — accompanied by yellow mottling, feathery patterns, or strong colour mosaic. Unlike aphid or drought curling, virus distortion does not reverse when conditions improve. Affected plants are also typically stunted. Remove and destroy infected plants to prevent aphid-mediated spread to healthy plants. There is no cure.

Cold or frost damage

Sweet potato foliage is very sensitive to cold. Even light frost or prolonged cold spells (below 10°C) cause the leaves to darken, droop and curl downward. If the damage is from a single cold night, the plant often recovers when warmth returns, though affected leaves may remain distorted. If cold exposure is ongoing, growth stops entirely. Protect with horticultural fleece in cool periods and do not plant out until minimum night temperatures are reliably above 10°C.