Amiudake

The Amiudake (アミウダケ) is a lethal species of mushroom that grows in the Sakura Kingdom (originally Drum Kingdom). Anyone who ingests the fungus will die an hour after consumption. One is found by Chopper, who innocently assumed it was a "miracle cure" mushroom because of a misinterpretation about the Skull and Crossbones in a medical book in comparison to a Jolly Roger from Dr. Hiluluk, to cure his fatal disease. Dr. Hiluluk, who knew the mushroom was poisonous, made a soup out of the mushroom in his loving gratitude for his surrogate son, and then chose to commit suicide, rather than letting the poisonous mushroom Chopper gave him finish him off.