Poison hemlock is spreading around Franklin County

Written by Jim Hook/The Chambersburg Public Opinion | Jun 14, 2018 8:45 AM

John Schwartzer, Franklin and Cumberland counties forester, stands in a field of poison hemlock. Poison hemlock grows wild along the side of the road in the 4000 block of Molly Pitcher Highway, Marion. Conium maculatum, or poison hemlock, is a highly poisonous flowering plant in the carrot family. (Photo: Markell DeLoatch, Public Opinion)

(Chambersburg) -- The weed can give you a rash if you brush against it.

It can kill you if you swallow it.

Poison hemlock is hiding in plain sight along roads and in fence rows. Farmers have mistaken it for giant hogweed, gardeners for Queen Anne's lace.

"It's spreading pretty rapidly," said John Schwartzer, service forester with the Pennsylvania Department of Conservation and Natural Resources. "It's one of the most toxic plants in North America."

Franklin County Commissioner Robert Thomas is ringing the alarm.

"This can be very dangerous," Thomas said. "It's growing up and down Interstate 81. It can also be next to manicured yards where children might play. It's everywhere."

"The railroads are all covered in it," Schwartzer said.

Ingesting the plant can be fatal. There is still no antidote for the poison that Greek philosopher Socrates chose to for his death sentence nearly 2,400 years ago.

"It paralyzes the lungs," Schwartzer said. "If you're not on a respirator, you die pretty quickly."

Thomas said the plant can pose problems for first responders helping accident victims on the roadside and for dairymen who unknowingly bale the plant with their hay.

Thomas and other local officials met Wednesday at a patch of poison hemlock growing along Molly Pitcher Highway (U.S. 11) in Guilford Township. A year ago, the area had about a dozen plants, according to Thomas. This year, 6-foot tall white flowers extend for more than 100 feet along the Pennsylvania Department of Transportation right of way.

Government, as well as property owners, have a role in controlling the weed, Thomas said.

"You've got to increase the awareness first," Thomas said. "This is just the beginning. We need to come up with a plan."

"Our guys are seeing it all around," Antrim Township Manager Brad Graham said. "They aren't hitting it with weed eaters. They aren't trained to deal with it."

One plant can produce more than 30,000 seeds, according to DCNR fact sheet on poison hemlock. Seeds can adhere to farm machinery, clothing and fur. The weed can establish itself quickly, particularly in disturbed sites.

Because it's a biennial, poison hemlock grows for two years. The second year it flowers and produces seeds.   

If you cut the plant too early, poison hemlock can produce another flower head, Schwartzer said. Cut it too late, you have the seeds.

The plant should not be composted because its seeds may survive the heat process. They should not be burned because the smoke may trigger asthma. They should be bagged and placed in the trash.

Hand-pulling works best for wet soils with small patches, according to DCNR. Removal of the entire root system is not necessary. Wear gloves, long sleeves and long pants, Schwartzer said. Wear a face shield if you're using a weed trimmer.

"If you get the sap on your skin it can cause re-occurring rashes," Schwartzer said.

Sap entering through a cut or your eyes can cause poisoning.

All parts of the plant are poisonous, but especially roots and seeds, Schwartzer said. The plant remains toxic for several years after being pulled.

The weed in recent years has a taken root in Franklin County, but local officials are at a loss to explain why.

Native to the Mediterranean region, poison hemlock has spread across the world. It was introduced to the U.S. from Europe in the 1800s as an ornamental.

The local problem came to Thomas' attention a year ago when he spoke with DCNR foresters about enhancing the county's Eco-Park on Franklin Farm Lane. Schwartzer noticed the tall weeds flowering in the park.

"I like to point it out to everyone I see," Schwartzer said.

 "Now that I knew what it was, I saw it everywhere," Thomas said.

The county sprayed herbicide to control the patch in Eco-Park, he said.

Eradicating the weed may take several sprayings over several years, according to DCNR. A spray that kills broadleaf weeds, rather than a broad spectrum herbicide such as Roundup, may be a good choice because other plants will grow in the weed's place, according to Schwartzer.

"Most poison hemlock deaths (in humans) are a result of wild foraging," Schwartzer said.

The weed has been mistaken for the "wild carrot," also known as Queen Anne's lace. The plants are found in the same habitats.

"The wild carrot is fuzzy and does not have that horrid smell," Schwartzer said.

Poison hemlock also has hollow, purple-spotted stems.

Livestock hungry enough to eat the plant in a paddock, or by finding it in their hay rations, die within two to three hours, according to Schwartzer.


Hemlock poisoning symptoms may include:

  • Stimulation of the central nervous system, then depression or paralysis of CNS
  • Vomiting
  • Trembling
  • Problems in movement
  • Rapid heart rate, then slow heart rate
  • Rapid respiration
  • Loss of speech
  • Increased salivation
  • Urination
  • Nausea
  • Convulsions
  • Coma
  • Death

This story comes to us through a partnership between WITF and The Chambersburg Public Opinion

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