Conium maculatum is a widely distributed cosmopolitan species native to Asia, Europe and North Africa; the species has been broadly introduced as an alien species throughout North America and other world regions. This perennial herb is typically found on poorly drained soils, particularly in riparian zones, ditches, and other surface water. It also appears at road verges, perimeters of cultivated fields and waste areas.

Known by the common name Poison hemlock, the species contains coniine, a powerful neurotoxin that can be lethal to humans and all classes of livestock. This member of the carrot family can reach a height of three meters. The stem is generally purple-spotted or streaked; the widely ovate leaves are typically 2-pinnate and are 15 to 30 centimeters in length. Inflorescences are much-branched.