Wells Lawn Care & Landscaping Logo
Get Custom Quote!

Poison Hemlock:
A Potentially Deadly Invader

Today, we want to shed light on a concerning plant known as poison hemlock. Originally brought to North America as a garden ornamental, it is originally from Europe and belongs to the Parsley family.

A Spring Emergent

In a recent Purdue Pest & Crop newsletter, experts Bill Johnson and Marcelo Zimmer highlighted the characteristics of poison hemlock. This noxious weed emerges early in the spring, typically around late February to early March. The plant’s major threat lies in the toxicity of its chemical compounds, which can be fatal if consumed by livestock or humans. Additionally, it can take away from the beauty of any landscape.

Where to look for Poison Hemlock

According to Purdue Extension’s fact sheet, Poison Hemlock lurks along roads, streams, trails, and ditches. Experts point out that poison hemlock is a biennial weed. This means that during the initial year of growth, it develops as the size of a short and small herb. But in the second year, its growth accelerates to a towering height of three to eight feet! Interestingly, it is often not noticeable until the reproductive stage of its second year.

Deadly if Ingested

But here’s the alarming part: poison hemlock contains five toxic alkaloids that can be deadly if ingested. The alkaloids may also seep through the skin, so if you ever find yourself hand-pulling poison hemlock, it is important to wear gloves. If consumed, symptoms of toxicity may include nervousness, trembling, and loss of coordination, followed by depression, coma, and, in severe cases, death. Initial symptoms can appear within a few hours of ingestion.

Thankfully, cases of poisoning from poison hemlock ingestion are rare. The plant’s mousy odor makes it unappetizing to both livestock and humans. Consumption and toxicity in animals usually happen in poorly managed or overgrazed pastures, where animals resort to grazing poison hemlock due to the lack of desirable forage.


Controlling poison hemlock with herbicides is most effective when applied during the plant’s first year of growth or before “bolting” and flowering in its second year. The closer it gets to the reproductive stages, the less effective the herbicide becomes. For roadside ditches, pastures, and waste areas, herbicides containing triclopyr or triclopyr prove most effective. Together we can safeguard our beautiful landscapes from the harmful effects of poison hemlock!



Mon – Fri: 7:30 am – 5 pm


575 W Simpson Chapel Rd,
Bloomington IN, 47404