Why Do Potatoes Turn Green?

Light triggers greening and bitter glycoalkaloids. Cut away green parts — or discard heavily greened tubers.

Green potatoes are a light problem — in the garden and in storage.

What causes greening?

When tubers are exposed to light, they produce chlorophyll (the green color). The same conditions are associated with higher glycoalkaloids such as solanine, which taste bitter and can be toxic in quantity.

Maryland Extension: cut out and discard green portions. Clemson: green portions are poisonous, bitter, and contain an alkaloid — cut off and discard before using. UMN: remove green areas; do not eat potatoes with extensive greening.

In the garden

Greening usually means hills washed away, shallow tubers, or insufficient mulch. Fix with better hilling or deeper cover when using the straw-growing method.

In storage

Any bright pantry or windowsill will green potatoes. Use the conditions in the potato storage guide and keep containers opaque and completely dark.

Can you eat them?

Small green patches: cut away generously beyond the green zone
Widespread greening or bitterness: discard the tuber
When unsure, throw it out — potatoes are not worth a food-safety gamble

Prevention beats triage: darkness from harvest onward, after a short soil-drying period.