Poison hemlock (Conium maculatum) is among the most deadly plants in North America. This non-native invasive weed contains highly toxic piperidine alkaloid compounds, including coniine and gamma-coniceine, which cause respiratory failure and death when ingested by mammals.
Poison hemlock is native to North Africa and Eurasia including Greece. It's the plant behind Socrates' famous last words, "I drank what?" Or, maybe it was, "don't try this at home." Just kidding. In fact, it was the plant used to poison...