Castor Bean is the most poisonous in the world and holds top position in this list. Castor Bean comes from the Euphorbiaceae family and is the sole species in the monotypic genus, Ricinus, and subtribe, Ricininae. Known for producing castor oil, this plant grows 3 to 30 ft. tall and is indigenous to the southeastern Mediterranean Basin, Eastern Africa, and India. The seeds from the castor bean plant are poisonous to people, animals and insects. Ricin, found in the seeds of castor beans, is more dangerous than snake venom and cyanide but only if inhaled.
Endemic to Indonesia, Rosary Pea grows in tropical regions around the world. The plant is best known for is seeds, which are used as beads and in percussion instruments. The attractive seeds of Rosary Pea is highly toxic due to presence of abrin, which is amongst one of the most effective poisonous substances recognized to man.