Gardening Fast Facts: Green Potatoes
What causes potatoes to turn green? The answer is a bitter-tasting chemical called solanine. Solanine is produced when the potatoes are exposed to sunlight. Even fluorescent lighting at the supermarket can make them turn green.
As potato plants grow, we hill them by pulling up additional soil around the plant. This enables the tubers to develop and expand, and prevents them from poking through the soil and turning green from the sun. Heavy rains can uncover potatoes near the surface, so it's a good idea to check your potato crop after a storm.
Solanine is toxic if consumed in large quantities, so cut away and discard any green portions of potato before you cook with them. When storing potatoes, be sure to keep them in a place where they won't be exposed to light.