Deadly nightshade. Flowers and leaves of the deadly nightshade, Atropa bella-donna, a poisonous plant which has medicinal uses. Deadly nightshade is used as an antidote to toadstool or mushroom poisoning. It dilates the eyes, stimulates the central nervous system and causes the heart to beat rapidly. Deadly nightshade preparations should not be taken by people with heart problems or psychological problems (neuroses). Deadly nightshade is a perennial plant which grows in shady woods in areas of Britain and Europe. The parts used are the leaves and roots which are gathered in May and September respectively.