Poison hemlock is invasive


Q . A gardener recently brought in a plant that I soon realized was the invasive poison hemlock (Conium maculatum). Are you aware of any more of these plants in Mahoning County? Is it actively growing right now?

Drew from Youngstown

A. Yes, this plant is rather common now, unfortunately. About 10 to 12 years ago, we began seeing this along railroad areas of southeastern Ohio. It is in every county in Ohio now. It is commonly seen along interstates and back roads, as well as along railroad beds and at the edges of farm fields.

It is a biennial, so it is actively growing now. It is green all winter. I see it all over Mahoning County, especially in February and March when its green mounds are so apparent along ditches and railroad tracks. These green mounds are up to 1 inch high and much greener than other plants during the winter months. During the summer months, the plant can get around 10 feet tall!

Poison hemlock is in the parsley family and resembles wild carrot, commonly called Queen Anne’s Lace. It is commonly called poison hemlock because it is indeed poisonous! This is the plant that famously killed Socrates, the Greek philosopher.

All parts of poison hemlock are toxic, especially the young leaves, stems and seed. The toxic alkaloids, including coniine and gamma-coniceine, cause respiratory failure and death when ingested by humans and animals.

Control options for this plant include mechanical removal or herbicide application. Pulling is difficult due to the 10-inch-plus taproot. The sap of the plant is a skin irritant, so clothing that covers skin should be used when handling the plant or using a weed trimmer for control.

To see pictures and learn more about this invasive plant, go to: http://go.osu.edu/poisonhemlock.

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Call the office hotline at 330-533-5538 to submit your questions. Regular clinic hours began April 4, on Mondays and Wednesdays from 9 a.m.-noon.

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