Water hemlock (genus Cicuta) is one of North America’s most poisonous plants, known for its extreme toxicity. Understanding its presence and characteristics is important for public safety, helping prevent accidental exposure and serious harm.
Where Water Hemlock Grows
Water hemlock is native to temperate regions of the Northern Hemisphere, found across North America and Europe. In North America, its distribution spans widely across the United States and Canada, from northern Canada to southern Mexico.
Several species of Cicuta contribute to this broad distribution. For instance, Cicuta maculata, known as spotted water hemlock, is most widespread throughout North America. Cicuta douglasii is found in the northwestern United States and western Canada, while Cicuta bulbifera is found across northern North America. Cicuta virosa has a circumpolar distribution, found in northern Eurasia and northern North America.
Typical Growing Environments
Water hemlock thrives in consistently moist or wet environments. It frequently grows in wet meadows, marshes, swamps, and along the banks of streams, rivers, and ponds. It is also found in ditches, including irrigation and roadside ditches.
It flourishes in poorly drained soils and can even grow directly in water. Its affinity for watery habitats makes it a common sight in low-lying areas and floodplains. This specific habitat requirement makes its presence predictable in certain landscapes.
Recognizing Water Hemlock
The plant is a perennial herbaceous plant, growing up to 8 feet tall with stout, erect stems that are often hollow, especially in the lower portion. These stems can be smooth and green, sometimes displaying purple streaks or blotches, particularly near the base.
Its leaves are fern-like, divided multiple times into narrow, toothed, lance-shaped leaflets. A key identification feature of water hemlock leaves is that their veins terminate in the notches between the leaf tips, rather than extending to the tip itself. The plant produces small, white flowers arranged in umbrella-shaped clusters, known as umbels, typically appearing in spring or early summer.
At the stem’s base, it has thickened, tuberous roots with distinct horizontal chambers. When sliced, these chambers are visible and often contain a yellowish, oily liquid that turns reddish-brown upon air exposure and emits a raw parsnip-like smell. While plants like wild parsnip or wild carrot can appear similar, careful examination of leaf venation and root structure helps differentiate water hemlock.
Understanding Its Danger
Water hemlock is one of North America’s most toxic plants due to cicutoxin, a potent neurotoxin found throughout all parts. The highest toxin concentration is in the roots, particularly in early spring. Ingestion of even a small amount, like a 2-3 cm root portion, can be fatal to adults and livestock.
Cicutoxin acts on the central nervous system, causing rapid, severe symptoms within 15 to 90 minutes of ingestion. Initial signs include drooling, nausea, vomiting, stomach pain, followed by muscle tremors, delirium, and violent convulsions. These seizures can lead to respiratory failure and death. Its rapid onset and symptom severity make water hemlock poisoning a serious medical emergency.