Potatoes that have green skin spots, are moldy or develop sprouts are potentially bad to eat. While moldy or mushy potatoes should be discarded, it is possible to save a potato with a green skin spot or sprout if this part is completely cut away.
It can be safe to eat potatoes from which the skin spots or sprouts were removed. However, if the green color extends below the potato skin, it is wise to throw the potato away. The green color is a sign of a poisonous substance called solanine that can potentially cause potato poisoning in people, according to the National Institutes of Health.
To keep potatoes from spoiling, it is useful to store them properly. An ideal storage place is a dark and cool area to extend their shelf life.