The yew plant is found all over the world and has a rocky history. Ancient cultures referred to this plant as the “tree of death,” because it may cause cardiac arrhythmia if ingested. It will completely stop your heart and cause death. Animals are very susceptible, and if they ingest yew, they’ll die within 24 to 48 hours. Its poison comes from its highly toxic alkaloids, which are found in high concentrations of the leaves in wintertime (Mount Sinai).