Atropa belladonna

Atropa belladonna, also known as deadly nightshade, was a plant native to Earth which contained the poison atropine. Belladonna was used to poison the water supply of the Sense Sphere by crazed humans when the First Doctor, Ian Chesterton and Susan Foreman arrived in the 28th century. During their stay, Ian was poisoned by this water, but the Doctor developed a cure for Ian and the afflicted Sensorites. (TV: The Sensorites)

Graham O'Brien read about deadly nightshade and its Latin name in garden-centre catalogues. (PROSE: The Secret in Vault 13)