Periodically add more straw to protect the developing tubers. At harvest time, just pull the straw back. Whatever method is used for growing and storing potatoes, the tuber should not receive light. When potato tubers are subjected to light they will turn green and will also increase the amount of a toxic chemical called solanine. All potatoes contain small amounts of alkaloid compounds usually just referred to as solanine.
Potatoes are in the same family as the poisonous plants of belladonna and nightshade.
High doses of solanine can kill. Lesser doses can cause gastrointestinal problems of nausea, diarrhea and vomiting to neurological problems of drowsiness and shortness of breath. Green potatoes could have 4 to 5 times the maximum amount of solanine considered safe. Since solanine is in the flesh, peeling does little to reduce concentrations. Green potatoes should not be eaten and should be deposited in the nearest compost pile.