Why Are My Sweet Potato Tubers Cracking and Splitting?

Sweet potato tubers with longitudinal cracks running along their length, or irregular surface fissures and splits, look damaged and are more vulnerable to disease entry during storage — though most cracked tubers are entirely edible. The cracking usually originates in the growing season rather than at harvest or during storage, and understanding which cause is responsible helps you prevent it in future crops.

Uneven watering — the most common cause

When a sweet potato tuber experiences a period of drought (slowing or pausing growth as the tuber's outer skin hardens), followed by heavy watering or significant rain (stimulating rapid water uptake and internal expansion), the skin cannot keep up with the sudden internal growth and splits. This is exactly the same mechanism that causes tomatoes to crack. The solution is consistent soil moisture throughout the growing season — avoid allowing the soil to dry out completely, then watering heavily. Apply mulch to buffer moisture fluctuations.

Compacted or stony soil

In compacted soil, the expanding tuber meets resistance that forces it to crack or deform rather than expand smoothly in all directions. Stones in the root zone produce similar irregular cracking and deformation as the tuber grows around them. Prepare the bed thoroughly to at least 40 cm depth, removing all stones and breaking up compaction before planting. In very stony or compacted ground, raised beds are the most reliable solution.

Root knot nematode damage

Nematode feeding on tuber tissue causes surface cracking, corking, and protrusions — irregular damage distributed across the tuber surface rather than the clean longitudinal cracks of water stress. Check the fine roots for bead-like galls; if present, nematodes are the cause. Manage through rotation and suppressive cover crops.

Harvest timing

Leaving tubers in the ground too long after the vines have died back — especially in wet autumn soil — allows the skin to deteriorate and tubers to reabsorb moisture unevenly, leading to surface cracking. Harvest promptly after the vines die or before the first frost, even if you had hoped to leave them longer. Cracked tubers used promptly after harvest are fine to eat; they deteriorate faster in storage so use them first.