Poison Hemlock

Poison hemlock (Conium maculatum) and wild parsnip (Pastinaca sativa) are two of our nastiest non-native weeds found in Ohio. Poison hemlock is one of the deadliest plants in North America. Wild parsnip can produce severe, painful blistering. Both are commonly found growing together.

Poison hemlock is a non-native biennial weed that spends its first year as a low-growing basal rosette; the stage that is currently very apparent. Targeting this stage for control will eliminate the first-year rosettes and prevent the development of the towering flowering stage.

Poison hemlock and wild parsnip are two of our nastiest non-native weeds found in Ohio. Poison hemlock can kill you while wild parsnip may make you wish you were dead. Both are commonly found growing together and continuously wet conditions caused both to flourish this growing season. The size of some infestations has been remarkable. Poison hemlock produces white flowers on stalks that create a more rounded look; perhaps a bit more like an umbrella.  Wild parsnip has intense yellow flowers with the stalks producing a more flat-topped appearance.

Second-year wild parsnip plants are producing deeply grooved flower stalks topped by characteristic bright yellow blooms in southern Ohio. Landscape managers and gardeners should exercise extreme caution around this non-native invasive biennial plant.

Poison hemlock is a non-native biennial weed that spends its first year as a low-growing basal rosette; the stage that is currently very apparent. During its second year, plants produce erect, towering stalks and multi-branched stems topped with umbrella-like flowers. Mature plants can measure 6-10' tall and are prolific seed producers.

Poison hemlock is one of the most lethal plants found in North America. This biennial weed is now in full flower throughout much of Ohio. So, the clock is ticking on preventing seed production by this non-native invasive plant.

Poison Hemlock (Conium maculatum) is one of the deadliest plants in North America. This non-native invasive was imported as an ornamental in the late 1800s from Europe, West Asia, and North Africa. The plant contains highly toxic piperidine alkaloid compounds, including coniine and gamma-coniceine, which cause respiratory failure and death in mammals.

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.

 

TOXICITY:

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...

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.  The roots are more toxic than the leaves and stems; however, all parts of the plant including the seeds should be considered dangerous.  It is a common misconception that poison hemlock sap will cause skin rashes and blisters.  In fact, poison hemlock toxins must be ingested or enter through the eyes, cuts, or...

This non-native invasive weed is among the most deadly plants in North America.  This biennial weed spends its first year as a basal rosette and the second year as an erect, towering flowering plant that can measure 6-10' tall.  Despite its common name, poison hemlock is not a tree; it is a member of the carrot family, Apiaceae (formerly Umbelliferae).

 

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