Poison Hemlock thriving in Idaho communities, posing threat to humans and animals

Posted at 4:30 PM, May 11, 2019
and last updated 2019-05-11 22:42:08-04

BOISE, Idaho — While you're out and about enjoying the warm spring weather this Mother's Day weekend, be on the look out for a pesky plant called Poison Hemlock.

The dangerous noxious weed has been documented as being fatal to humans and all classes of livestock, and is now in full growth around the state.

Typically Poison Hemlock grows in riparian areas, stream banks, canals and ditch banks, and pastures, according to the Idaho Weed Awareness Campaign. It is a biennial plant meaning it grows for two-years. During the second year it flowers, seeds and then dies.

“This dangerous noxious weed presents an issue of public and animal safety. Poison Hemlock has been proven to be deadly to both animals and humans. It is so toxic that horses and cows literally can die within hours after eating this poisonous plant,” said Roger Batt, statewide coordinator for the Idaho Weed Awareness Campaign.

Poison Hemlock grows 3-8 feet tall with a smooth green stem, usually spotted or streaked with red or purple spots. The leaves are finely divided and lacy, resembling a “carrot-like” leaf. The weed has flowers that are small, white and clustered and resemble the spokes of an umbrella. The Poison Hemlock root is fleshy and white. When crushed, Poison Hemlock’s leaves and roots emit a rank, unpleasant odor often compared to that of a mouse or parsnip.

“There are documented cases where people have eaten Poison Hemlock because they mistook the weed for some type of wild parsley, dill or fennel,” Batt added. “Poison Hemlock roots are also mistaken for parsnips, its leaves for parsley or fennel, and its roots and seeds for wild carrots or anise.”

Though highly toxic, Poison Hemlock is very easy to control and eradicate with hand pulling and the use of herbicide treatments.

Always wear rubber gloves and protective clothing/gear when pulling this weed and place the plant into a plastic bag and dispose of it into a trash receptacle. When using an herbicide to control and eradicate Poison Hemlock, officials say to use an approved herbicide and always follow the label and safety instructions on that label.

Poison Hemlock, whose scientific name is Conium maculatum, is the plant from which juice was used by the ancient Greeks to kill Socrates.

Residents can also seek technical assistance to get rid of Poison Hemlock and other noxious weeds by contacting their County Weed Control Department. They can also log on to the Idaho Weed Awareness Campaign’s website and learn how to control and manage this noxious weed on the homepage of this website under Weed Control Alert.