CINCINNATI, Ohio – Spring rains are a blessing for any farmer. But as the moisture subsides producers are faced with a resurgence of unwanted poison hemlock and wild parsnip in and around their fields. Weeks of rain have spurred these unwanted plants to spread rampantly in Ohio, Indiana, Kentucky and throughout the Farm World readership area.

“Unfortunately, poison hemlock and wild parsnip are becoming more common throughout Ohio and many other states in the upper Midwest as well as states in the eastern U.S.,” said Joe Boggs, an assistant professor for The Ohio State University Extension. Boggs is an assistant professor in extension who specializes in trees, shrubs, non-native invasive pests and urban forestry.

“Worse, owing to the lack of awareness or poor management practices, these dangerous non-native weeds are increasingly being found growing in close proximity to people, which increases their risks to human health,” Boggs added.

Boggs said the trajectory over the last 15 years shows the appearance of both plants has been on a constant rise. Often the two are seen growing together.

“We all know to look for poison ivy, now we need to look for these weeds, too,” Boggs said. “Poison hemlock can kill you if you ingest the toxins, while wild parsnip may make you wish you were dead. Wild parsnip affects you on the outside, so you end up with almost a second-degree sunburn.”

Poison hemlock was imported into the United States as an ornamental in the late 1800s from Europe, West Asia and North Africa. Rogue plants remained relatively rare until around 30 years ago.

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 in its second year. The first year it’s a small rosette 6-8 inches tall. The second year, it bolts and that’s when it can get 6 feet tall.

“All parts of poison hemlock should be considered dangerous, including the leaves, stems and seeds,” Boggs said. “The roots are the most toxic part. The plant’s toxins can enter the human body through rubbing an eye or nose. Poison hemlock doesn’t cause skin blistering on contact. People sometimes eat the roots of wild carrot, called, Queen Anne’s lace, which bears a striking resemblance to poison hemlock.”

Parsnips have been cultivated as a root crop in Europe for centuries, perhaps millennia. It is theorized that the wild parsnip plants in Ohio represent “escapes” from cultivated types brought to North America from Europe and a “reversion” back to a wild type.

Wild parsnip is a biennial/perennial herb. The plant typically can grow up to 4 feet tall in an average year. It is common throughout the northern United States and southern Canada.

 “Don’t be so quick to cut down the wild parsnip. If you do mow it, if you do cut it off, you need to make absolutely certain that you are protected against the sap,” Boggs said. “There have been reports of people using weed eaters, using clippers and things of this nature, and have gotten sap on their legs and on their arms and then ended up in the hospital.”

The biggest warning, Boggs said, is there are no signs of either weed slowing their growth in the Farm World readership area. “Bottom line is they produce a lot of seed, so you can go from one plant to hundreds of plants in a very short period of time,” he said.

Livestock producers should beware of poison hemlock, too.

“Of the two, poison hemlock poses a real danger to livestock,” said Dr. Michelle Arnold, associate professor and ruminant veterinarian at the University of Kentucky. “Poison hemlock is toxic to a wide variety of animals, including cattle, sheep, goats, pigs, horses, birds and wildlife. Cattle will not eat wild parsnip but deer may feed on it, and birds and small mammals eat the seeds.

“Although cattle seldom eat hemlock, they will if no other forage is available, or if is incorporated in hay or silage. A common question is how much do cattle need to eat to kill them? Unfortunately, experts say, the answer is not clear-cut.”