There are four species of water hemlock in North America, all highly poisonous and native to North America: spotted (C. maculata), western (C. douglasii), bulblet-bearing (C. bulbifera), and Mackenzie’s (C. virosa).

Toxicity to Humans and Livestock

The four species of water hemlock contain cicutoxin, a highly poisonous, unsaturated alcohol with a strong, carrot-like odor. The highest concentration of toxin is found in the roots/tubers; however, it is also present in leaves and stems, especially early in the growing season. Leaves and stems lose most of their toxicity as they mature, but green seed heads remain poisonous.