See an earlier report on dangerous weeds in Ohio in the player above.

COLUMBUS, Ohio (WCMH) — One of more than two dozen weeds designated by the state of Ohio as noxious — poison hemlock — is likely beginning to flower in some central Ohioans’ yards. 

Although its clusters of white petals are attractive to the eye, every part of the plant is “highly toxic,” according to researchers at Ohio State University. The plant usually starts to show flowers between June and August. 

Poison hemlock was “relatively rare until 30 years ago,” but the weed is becoming more common in the state — too frequent to be fully eliminated, according to Ohio State University assistant professor Joe Boggs. 

Poison hemlock lifecycle, identifiers

The noxious weed is biennial. In its first year, the carrot family member will grow low to the ground in rosettes and might look like a wild carrot, but give off a more rank smell, Boggs writes. 

In its second year, it will grow much taller — towering anywhere between six and 10 feet tall. Its stems will bloom into flowers, and once it scatters its seeds for new weeds to grow, it will die. At this stage, poison hemlock can be mistaken for water hemlock, which is poisonous, and water parsnip, which is not. The trick in differentiating, according to Boggs, is the stem.

Poison Hemlock grows in Butler County, Ohio. (NBC4 Photo/Tony Mirones)

Poison hemlock stems are hairless and, most notably, are blotched with purple-colored circles or streaks, Boggs writes. 

Although Boggs writes that “poison hemlock is one of the deadliest plants found in North America,” humans have to either ingest poison hemlock toxins through their eyes, nose, or a wound to become poisoned.

Unlike poison ivy or poison oak, it won’t cause a rash — but you should still avoid touching it and contact emergency medical services if you think you’ve ingested its toxins. 

How to get rid of poison hemlock on property

State law mandates that property owners cut or destroy prohibited noxious weeds, including poison hemlock. The list of prohibited noxious weeds outlined in the Ohio Revised Code is available here.

Small infestations can be taken out by hand, if done properly — but by this time of year, Boggs writes that it is likely too late to just mow over poison hemlock or pull it, particularly if it is already towering.

An easier solution is to use herbicides. Although different kinds will work, OSU Extension has more information here about how those herbicides will affect the plants and grass surrounding a poison hemlock infestation and ways to get rid of the weed in general.