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Concern Grows as Poison Hemlock Spreads Uncontrolled

6/15/2013 7:00 AM
By Ad Crable Lancaster Newspapers

LANCASTER, Pa. — Poison hemlock — yes, the plant that was used to execute Socrates — is exploding across Lancaster County, worrying livestock owners, parents and naturalists.

The highly poisonous herb is another one of those non-native plants brought to the United States because it looked pretty, but it is now wreaking environmental havoc.

Over the last several years, hemlock, which can grow swiftly to up to 10 feet tall, has elbowed out such other unwanted foreign vegetation as ailanthus and Canadian thistle to become a dominant part of the scenery here along roadsides, pastures and field edges.

“I just think the whole county should be alert to this because it is spreading so rapidly, and I just hate to envision what it will look like five years from now if nothing is done, because it is just totally taking over,” said Roland Yoder, 77, a former biology and art teacher who lives at Landis Homes Retirement Community.

“I see that poison hemlock everywhere, and I have a concern about it,” said Jeffrey Graybill, of Penn State Extension’s Lancaster office.

PennDOT crews here have begun spraying roadsides with poison hemlock, said agency spokesman Mike Crochunis.

“It’s taken off,” said William Curran, a Penn State professor of weed science. “It’s just about everywhere between Lancaster and State College.

“If it becomes more common in hay or pasture fields, I think people would pay more attention,” he said. “I’m not sure if we’ve seen the tip of the iceberg.”

All parts of poison hemlock are extremely poisonous to humans and livestock, especially the seeds.

“Deaths have occurred from mistaking the roots for wild carrots,” warns a broadside by the state Department of Conservation and Natural Resources.

Fortunately, livestock generally don’t like the taste of the plant. It would likely be avoided in a pasture unless other vegetation had dried up or disappeared, experts said.

But with the rapid spread of the plant, local ag officials are worried that it is within easier reach of cows and horses on the edges of fields. The plant being cut and baled into hay is another concern.

“I have not heard of any human or livestock poisoning in the state yet with it, but I still don’t understand why we haven’t, actually,” Graybill said.

Jeff Stoltzfus, a farmer and the adult agriculture instructor for Eastern Lancaster County School District, said the plant killed a couple of horses in the county about 10 years ago.

Dr. Willard Stoltzfus, a large-animal veterinarian with Black Horse Animal Hospital, Kinzers, said he suspected hemlock poisoning in a few cases involving livestock 20 years ago.

Although several horses and livestock are poisoned each year in Pennsylvania from eating poisonous plants, the state Department of Agriculture has not received any recent confirmations of livestock poisoned by eating hemlock, said spokeswoman Nicole Bucher.

But, she said, “It does appear more prevalent this year than in past years. It’s definitely something we’re keeping an eye on and we’re concerned about, especially when it’s near fields and feedlots.

“We may consider listing it as a noxious weed, which would give us regulatory authority to stop its spread,” she said.

A poison hemlock distribution map by the USDA shows about half the counties in Pennsylvania being invaded by the plant.

The unwanted plant is native to Europe, western Asia and North Africa. It is in the same family as carrots, parsley and Queen Anne’s lace, and is sometimes mistaken for those plants with its white, lacy flowers. It is not related to hemlock trees that are native to North America.

It was introduced to the United States as an ornamental garden plant. As has happened with so many invasives, the plant spread into the wild. Now, it is running amok.

As with many other invasives, it crowds out native species.

Hemlock is a biennial plant. Those towering plants seen now with white flowers are ready to spread their seeds, then die.

A single hemlock plant can produce more than 30,000 seeds, which is why it has spread so rapidly and is a nightmare to control. This is why Yoder thinks there needs to be a major publicity campaign mustered to alert the public to its potential dangers.

“If you own any land, make sure you try to get rid of it,” he said.


Given the prolonged winter, have you been able to do any of your spring planting?

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