Potato plants provide plump tubers ready for baking or frying. According to the National Institutes of Health's Medline Plus site, the only edible part of the potato plant lies underground in the fully ripened tuber. All other parts--unripened tubers, stems, sprouts, leaves, fruit and roots contain toxins that will make you sick if you eat them. When the tubers come into contact with sunlight or fluorescent light, they begin to taste bitter, which the University of Illinois notes results from the formation of a toxic alkaloid in the tuber when it reacts with sunlight. Dark, cold storage will keep your potatoes tasting their best.
Pull or dig the potatoes out of the ground after the vines die. Cut the stems off the tubers with a knife and discard all parts of the plant except the tubers.
Scrub the potato tubers under running water with a scrub brush to wash off any dirt.
Optionally, peel the potatoes. Slice the potatoes into matchsticks, thin slices or leave whole.
Cook the prepared potatoes by boiling and mashing, frying in a pan with one to two tablespoons of oil or deep frying in three to four inches of oil or bake in the oven until tender.