Why Are My Sweet Potato Leaves Turning Yellow?

Sweet potato foliage should remain a rich, deep green throughout the growing season. When leaves begin to yellow — whether uniformly across the whole plant or in patches — something is limiting the plant's ability to produce chlorophyll. The underlying cause could be a nutrient shortage, waterlogged roots, pest damage, or a viral infection. Identifying which pattern of yellowing you are seeing helps pinpoint the right solution.

Nitrogen deficiency — uniform pale yellowing

A uniform fading from deep green to pale yellow-green across older leaves, progressing upward through the plant, usually indicates nitrogen shortage. Sweet potato is a hungry crop and in poor, sandy or heavily leached soils, the nitrogen supply runs out long before the tubers finish forming. Water in a balanced liquid fertiliser or apply a top-dressing of well-rotted compost around the base of the plants. Avoid high-nitrogen feeds in mid to late season as they push leaf growth at the expense of tuber development.

Overwatering and root problems

Waterlogged soil suffocates the roots, preventing them from taking up nutrients even when nutrients are present in the soil. Yellowing caused by overwatering tends to affect multiple leaves simultaneously, the soil feels persistently wet, and in severe cases the base of the stem may darken or smell of rot. Sweet potato must have excellent drainage — it evolved in warm, sandy soils and cannot tolerate waterlogged conditions. Allow the soil to dry somewhat between waterings.

Sweet potato virus disease

Several viruses affect sweet potato, most commonly Sweet Potato Feathery Mottle Virus and Sweet Potato Chlorotic Stunt Virus, which are spread by aphids. Virus infection causes irregular yellow mottling, feathery patterns, or bright yellow-green patches rather than the uniform yellowing of nitrogen deficiency. Affected plants are often also stunted and the vines may have distorted leaves. There is no cure — remove and destroy infected plants to prevent spread, and control aphid populations to limit transmission.

Natural lower-leaf yellowing

As sweet potato vines grow long and dense, the oldest lower leaves are shaded out by the canopy above them. These lower, innermost leaves naturally yellow and drop — this is normal and not a problem. If yellowing is confined to the oldest, most deeply shaded leaves and the rest of the plant is vigorous and green, no action is needed.