The pores on the garden potato, known as lenticels, become swollen and white. This gives the potato the appearance of having white bumps on its skin. The condition occurs when the potato is in the ground or after it has been stored.
Lenticels allow the potato plant to successfully breath. They function by allowing the plant to exchange oxygen and carbon dioxide, which aids the plant in both photosynthesis and respiration. All potatoes have lenticels.
Potatoes grown in overly wet soil or stored in wet conditions begin to grow a corky white substance around the lenticel. The substance occurs when the lenticels ability becomes impeded by the moisture in the soil and the potato's lenticels becomes clogged. The tissue around the lenticel begins to swell and burst out.
Potatoes suffering from swollen lenticels are safe to eat but do not store for an extended time period. They are more susceptible to soft rot during storage. The condition is somewhat reversible if the potato is no longer exposed to wet conditions.
Plant potatoes in well-draining soil and do not water excessively. Avoid storing harvested potatoes in an area with excessive condensation.