One of the 'deadliest plants in North America' is blooming. What to know about poison hemlock

GALION, Ohio – Poison hemlock, a dangerous weed that has only been in the Buckeye State for a few years, is in full bloom this week in North Central Ohio.

The hazardous plant is more visible in the area this year than ever before, according to Jason Hartschuh, Ohio State University Extension agent for Crawford County.

"It’s everywhere. You about can't drive U.S. 30 and not see it," Hartschuh said. "It keeps spreading by wildlife and by water and flood plains."

Poison hemlock started making news in 2019 when it was reported to have spread across southern Ohio. Now it's abundant across the state. The plant is also prevalent in Pennsylvania.

Dangerous if eaten

The plant can be deadly if eaten, said professors Joe Boggs and Erik Draper, in The Ohio State University's Buckeye Yard & Garden online blog.

"Poison hemlock is one of the deadliest plants in North America," they wrote. "Plants contain highly toxic piperidine alkaloid compounds, including coniine and gamma-Coniceine, which cause respiratory failure and death in mammals. The roots are more toxic than the leaves and stems; however, all parts of the plant including the seeds should be considered dangerous."

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The plant is in the carrot family, as is Queen Anne's Lace, and their similarities can make them hard to differentiate.

"The roots of wild carrot, or Queen Anne's lace (Daucus carota), are sometimes eaten raw or cooked," the professors wrote. "Unfortunately, they bear a striking resemblance to poison hemlock roots and misidentifications have been responsible for a number of accidental poisonings."

Not safe for animals, either

Farmers who have pasture land will want to keep an eye out for poison hemlock to ensure none of it is growing where their animals are grazing.

"Most of the time livestock are smart enough to not eat it," Hartschuh said. "Where we get into trouble is if we get a drought and everything else goes dormant and that's the only thing still green, they'll eat it."

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Hayfields are also at risk of becoming invaded by poison hemlock, and animals can still become sick if some of the plants make it into their bales of hay.

"It does lose some of its toxicity when it dries," Hartschuh said. "But it does still have toxins when it's dry."

Positive identifications increasing

Like parsley and other carrot family members, poison hemlock will have tiny white flowers that grow in clusters this time of year.

A big difference in the plants is that the stalk of poison hemlock is purple, according to Josh Dyer, director of the Crawford Park District.