Is it ok to eat potatoes that have turned green? A friend told me that they read on the internet that a green potato is poisonous and to immediately throw it out. He also said they taste bitter when green.
The potatoes with a green tint to the skin will taste bitter. If just a light green, then trim off the green skin or flesh and boil, bake or prepare as usual. However, with what I have been seeing in retail grocery stores lately on display, I would caution you to not automatically pick up potatoes for purchase that have turned very green. Typically if the potato has been exposed to light (sun light, fluorescent light, spots, etc.) it will convert the skin to Solanine, which if ingested in large quantities can be toxic. But, you’d have to eat much more than a single potato to feel ill.
Lately, bright green potatoes seem to be a lot more common than I ever remember. The Russet, displayed loose or in a bag can turn green in a matter of days when customer sales are slow or a store is not rotating the display to get rid of potatoes with soft spots, bruises, ugly shapes and greening. You may even see the effect of the light by turning a bag over and seeing the green tinge to the brown skin on the top and a normal brown/tan color on the bottom of the bags. The yellow flesh varieties, such as a Yukon Gold have a very thin skin and can turn green very quickly. While fingerlings, especially the Russian Banana variety, may have a select customer attraction to those willing to pay a premium price and tend to be sitting longer and also have a tendency to turn green quickly. When storing any potato at home it helps to keep them in a cool dark place.
Here is my “pay it forward” advice: If you see several green potatoes on display, do future shoppers and yourself a favor and ask the produce person to bring out more potatoes from the back storage area. The potato display should always look appetizing and fresh and “old stock” needs to be replaced, rather than sold to an unsuspecting customer that buys a green potato, cooks it and then doesn’t want to buy potatoes again because of the bitter taste.