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Poison Hemlock Spreading In Pa.

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Poison hemlock spreading in Pennsylvania

Updated: 9:48 AM EDT Jun 9, 2021

State agriculture officials are warning Pennsylvanians about an invasive and dangerous plant that's blooming right now.

The poison hemlock plant is poisonous to both people and animals.

Penn State Extension says the plant has a smooth, hollow stem and can be identified by purple spots on its stems.

It tends to grow near meadows and streams and smells like parsley when it is crushed.

Pennsylvania's botany and weed specialist says it spreads easily, and there are ways you can get rid of it safely.

"I do advise people to wear long sleeves, long pants, gloves if working with it-- Preferably don't mow it if you can avoid it because people can breathe in those particles," said Trilby Libhart, Pennsylvania botany and weed specialist.

The state also says another plant, the giant hogweed, has almost been eradicated in Pennsylvania, but experts say a lot of people mistake cow parsnip for it.                                                                                                                                                                                                                                            SEE VIDEO REPORT     ;    https://www.wtae.com/article/pennsylvania-poison-hemlock-spreading/36672792

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Poison Hemlock: Facts About this Early Season Weed

Poison hemlock resumes its growth early in the spring. Learn more about this weed that is widespread across the state.
Poison Hemlock: Facts About this Early Season Weed - News 


Poison hemlock as it begins vegetative spring growth. Source: D. Lingenfelter, Penn State Weed Science images

Plant family: Poison hemlock (Conium maculatum) is in the carrot or Umbelliferae family and the leaves and foliage resemble carrot and parsley.

Look-alikes: Wild carrot (also called Queen Anne’s lace), wild parsnip, spotted water hemlock, and purple-stemmed angelica can sometimes be confused with poison hemlock because they are in the same family and have some similar features. Cow parsnip and giant hogweed are also in the same family; however, they are much larger in stature and should not be easily mistaken with poison hemlock.

Lifecycle: Poison hemlock germinates from seed and is a biennial plant with a basal rosette of leaves during its first year. Once it overwinters, in late April/early May, it bolts into an erect branched plant producing prominent white flowers in an umbel generally in June and July. It sets and drops seeds soon after. This weed only reproduces by seed and its taproot dies as the main plant desiccates.

Vegetative stage of poison hemlock. Note purple blotches on the main stem. Source: D. Lingenfelter, Penn State Weed Science images.

Characteristics: In addition to its fern-like, glossy green, lacy leaves, the plant has a hairless, hollow main steam with purple blotches/spots which branches. Its large flower structures are composed of many smaller white flowers. Plants typically grow 2 to 6 feet tall and have a parsnip-like odor when the leaves are crushed.

Poison hemlock at flowering. Source: D. Lingenfelter, Penn State Weed Science images

Poisonous traits: The sap can cause dermatitis (skin irritation) on some people. So be sure to wear protective clothing and gloves when handling the plant or when weed-whacking. It is poisonous when ingested by humans and livestock. The plant contains several closely related pyridine alkaloids with the main one being coniine, a colorless, volatile, and strongly alkaline oil. All parts of the plant are poisonous, and some studies have shown toxicosis at 0.25% fresh wt. (of the animal’s weight) for horses and 0.5% for cattle. That would be 2.5 to 5 lb. of material per 1000 lb. animal. Mature seeds are the most poisonous. Significant poisoning can result in muscle paralysis and suffocation.

Habitat: It grows along roadsides and in no-till fields, fencerows, pastures, fallow areas, and waterways.

Control: Individual plants can be easily dug out with a shovel. Larger infestations can be cut with a mower or string trimmer or may require the use of a herbicide. Several herbicides are effective for control. Herbicide applications are most effective when they are sprayed in the fall when poison hemlock is in the rosette stage or before it bolts in the spring. Effective herbicides include 2,4-D + dicamba, Crossbow (2,4-D+triclopyr), or glyphosate as a spot treatment.

Other interesting facts: Poison hemlock is native to Europe, northern Africa, and western Asia and was introduced to North America as an ornamental garden plant. In the annals of history, it was noted that the Greek philosopher Socrates chose to drink poison hemlock tea for his execution.

Additional Poison hemlock information:

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I have whined steadily about this stuff which is extremely toxic to animals and mildly caustic to humans. At an early stage, it can be sprayed pretty easily, but as it spreads over miles of roadway, then it becomes a water contaminant problem to be dealt with.  Farmers can be losing animals to it or even pets if they seem to like chewing on it.

It's one of those "ignore it as long as possible" situations.



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Many of the plants we grow in our gardens are poisonous. You can't eradicate them all. Don't eat the weeds or the garden plants if you don't know what you are doing. A word to the wise. Queen Anne's lace blooms much later and has that little black/purple floret in the center. Enjoy it. It is very pretty. 

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  • 2 weeks later...

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

Poison Hemlock can cause blisters if touched or death if eaten

Zach Tuggle
Mansfield News Journal

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.

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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.

"It’s a dead giveaway," Dyer said. "The other ones are typically green."

From a distance, though, the various related plants can be hard to distinguish.

"There are a few different species out there that look similar," Dyer said.

That resemblance made most sightings in years past false alarms. But as poison hemlock has taken hold in North Central Ohio, most calls the naturalist has received have led to positive identifications.

"It's really taken off," Dyer said. "I don't know if it's wind or water-driven, but it seems like it likes being near water."

Flowers only in its second year

Poison hemlock is a biennial, meaning it takes two years to complete its biological lifecycle. The plant is hard to identify during its first year.

"It flowers on the second year," Hartschuh said. "The first year it's a small rosette six to eight inches tall. The second year, it bolts and that's when it can get six feet tall."

Fortunately for those attempting to control its population, the plant dies after the second year – propagation can only happen through the plant's seeds, not via its root system.

"Things that are a biennial can be controlled much better than things that are perennials," Dyer said. "You just have to be diligent and knock it back."

Painful skin irritant

But hacking away at poison hemlock can be a very painful task if the proper precautions are not taken.

"It can cause blisters," Hartschuh said. "If you're out weed eating, you should wear splash-proof goggles and maybe a face shield because you don't want that juice getting on your lips or in your eyes."

If the plant has already started to flower, then cutting the heads off and placing them inside a plastic bag to be thrown away will help reduce the spread of seeds.

One of Dyer's colleagues recently tried to eradicate some poison hemlock and discovered the hard way how dangerous the plant really is.

"They got really bad blisters from it," Dyer said. "I assume it's like other irritants – it depends on the individual and how they respond to it."

Poison ivy is a good example he said. Some people are deathly allergic, while others only become mildly irritated.

His final advice was to leave the chopped plants in a pile, or take them to the landfill – just never torch them, regardless of the situation.

"I wouldn't burn it," Dyer said. "Like with poison ivy, if you burn it the oils will get in the air and you can get poison ivy in your lungs. I don't know yet if poison hemlock is the same, but I would not want to risk it."                                                                                                                                                          SEE VIDEO REPORT    ;     https://www.usatoday.com/story/news/nation/2021/06/21/poison-hemlock-deadly-weed-blooming-across-ohio-how-spot/7767718002/

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