Poison Hemlock, Conium maculatum, is sometimes known as Hemlock. All parts of this plant are very poisonous, do not ingest. The ancient greeks administered the juice from this plant, as a poison, to execute criminals. Socrates died in this manner. Note: Poisonous Plant. Hemlock is native to Europe is adaptable to most soils and conditions. White flowers in spring. Frost resistant but drought tender. A biennial plant, growing to 1.5m x 1.0m.