Poison hemlock is spreading across the US. Here’s how to get rid of it

The plant can cause symptoms leading to death in mammals

A roadside plant is posing a potentially deadly risk to Americans after it was found to be growing rapidly in unmanaged areas.

Poison hemlock, also known as Conium maculatum, is poisonous to humans when ingested through the eyes, nasal passages or cuts in the skin. It contains highly toxic compounds known to cause respiratory failure and death.

Humans can be affected by the poison if they come into contact with the plant bare-handed. All contact should be avoided, and poison hemlock should never be mowed or burned.

According to the United States Department of Agriculture (USDA), Poison hemlock starts growing in the early spring and “usually grows for two years.” It’s found at “roadsides, on edges of cultivated fields, along creek beds and irrigation ditches, and in waste areas.”

The Tennessee Department of Agriculture noted that poison hemlock can be identified by its tall, hollow stems with purple spots and small white flower clusters forming.

So, what’s the best way to get rid of Poison hemlock? According to the University of California Agriculture & Natural Resources, there are a few different ways to control the plant.

Poison hemlock can be found at roadsides, on edges of cultivated fields, and in waste areas (Getty Images)

Once identified, remove individual plants by hand pulling, hoeing, or applying a herbicide, which is a pesticide designed to kill unwanted plants. Of course, this should be done with gloves.

Hand removal is best for small infestations, with the entire taproot being removed when the plant is pulled out to prevent regrowth. Herbicides such as 2,4-D, triclopyr, and glyphosate could be the most effective in stopping Poison hemlock from growing more.

Glyphosate is “nonselective,” meaning it will kill any plant that it comes in contact with, so use it with caution to minimize “mortality of desirable plants that might help suppress new poison hemlock seedlings,” according to UC Agriculture & Natural Resources.

However, “herbicides should be used only on seedlings or small rosettes,” and not on plants that are fully grown. Treating Poison hemlock with herbicides may require repeated applications for a couple of years, until “the seedbank has been significantly depleted.”

In addition, “solid carpets of hemlock seedlings” aren’t uncommon after soil disturbance, so “plowing or repeated cultivation of newly germinated plants will prevent poison hemlock establishment.”

Hemlock poisoning can occur in humans if they accidentally ingest the plant, which is often mistaken for wild carrot, wild parsnip, or wild parsley.

The poisoning could be fatal, with symptoms — including vomiting, sweating, excess salivation, restlessness or confusion, and rapid heartbeat — occurring almost immediately after eating the plants, according to the Cleveland Clinic.

Although there isn’t an antidote for the poisoning, your doctor will offer treatment based on your symptoms.

Poison hemlock is also extremely toxic for livestock, including sheep, cattle, swine, or horses. Domestic animals are poisoned by eating small amounts of the plant.