Forage Management: The Dangers of Poison Hemlock in Pastures and Hayfields

By Dr. Bruno Pedreira

Poison hemlock (Conium maculatum) is a toxic plant that poses a significant risk to  livestock. Its presence in pastures and hayfields can result in fatal poisoning if consumed. As cattle producers, it is crucial to be aware of how to identify poison hemlock, understand its toxicity, and take proactive measures to eliminate it from pastures.

How to Identify Poison Hemlock

One of the key challenges in managing poison hemlock is its resemblance to other non-toxic plants, such as Queen Anne’s lace (Daucus carota). Both plants share similar white, umbrella-shaped flower clusters (Fig. 1). However, there are distinct differences that can help differentiate poison hemlock from harmless look-alikes:

• Purple Spots on the Stem: Poison hemlock has purplish spots or streaks on its smooth, hollow stems (Fig. 2). This is a crucial feature for proper identification.
• Leaf Shape: Poison hemlock leaves are fern-like and often have a strong, unpleasant odor when crushed.
• Size and Growth Pattern: Poison hemlock can grow up to 8 feet tall, with branched stems and clusters of white flowers, typically appearing in late spring.