Why Are My Potatoes Hollow Inside?

You slice open a big beautiful potato only to find an empty cavity at the centre — sometimes smooth-walled, sometimes with a brown discolouration around the edges. This is hollow heart, a physiological disorder rather than a disease. There are no pathogens involved and no infection to spread, which is some comfort. The hollow potato is still perfectly edible once the cavity is cut away, but it represents wasted growing potential. Understanding what causes hollow heart makes it easy to prevent in future seasons.

What causes hollow heart

Hollow heart forms when the outer flesh of the potato expands faster than the interior can fill in, leaving a gap at the centre. This happens when growth is erratic or too rapid — particularly in large tubers that are growing very quickly during periods of high soil moisture or overfeeding. The very largest tubers in any crop are always most susceptible because a large tuber requires more internal tissue to fill its greater volume, and any disruption to cell division at the centre results in a gap. Heavy rain following a dry spell — the same boom-and-bust cycle that causes cracking — is a common trigger.

Spacing and plant density

One of the most consistent risk factors for hollow heart is wide spacing combined with low plant density. When a potato plant has very few competing tubers — because seed spacing was wide or because few eyes developed — individual tubers grow very large very quickly. Oversized tubers are far more prone to hollow heart. Planting at the recommended spacing (typically 30–35 cm for earlies, 35–40 cm for maincrops) and choosing a seed size that gives two to three healthy eyes per set produces more tubers per plant at a moderate, even size. These smaller, steady-growing tubers are much less likely to develop hollow centres.

Watering consistency

Irregular watering is the other major factor. A dry period when tubers are actively sizing followed by sudden heavy rain or irrigation triggers the rapid expansion that causes hollow heart. Consistent, regular watering — particularly through the tuber bulking phase which runs from about eight weeks after planting until harvest — keeps growth steady. The critical watering window is when the plants are flowering, which coincides with active tuber bulking. During this period, aim to keep the soil consistently moist but not waterlogged, watering before the soil dries out rather than after.

Is hollow heart edible?

Yes. Cut away the hollow section and any discoloured tissue around it and the rest of the potato is completely fine. Hollow heart has no effect on the taste or nutritional value of the surrounding flesh, and there is no infection or toxin involved. You cannot tell from the outside which potatoes have hollow heart — it is only revealed when you cut them. Very large potatoes are the most likely candidates, so if you want to avoid wasting them, use the biggest tubers first and slice through the centre before committing to a cooking method.