Poison Hemlock is one of about 30 plants that can poison livestock.

Being able to identify poisonous plants allows livestock producers to avoid the loss of animals in their herds and flocks. I have seen an increase in Poison Hemlock in our area and want to remind producers of this threat to domestic animals.

Poisonous plants are a major cause of economic loss to the livestock industry. Each year these plants adversely affect 3% to 5% of the cattle, sheep, goats and horses that graze western ranges. Sometimes these losses are large enough to cause the ranch financial difficulty.

There are a number of plants that have toxicity. Some plants are toxic at certain stages of growth and some are toxic throughout their lifecycle.

Two of the most toxic plants in the Pacific Northwest are Poison Hemlock and Western Water Hemlock.

Poison Hemlock, Conium maculatum, which resembles a carrot plant, is often mistaken for Wild Carrot.

Poison Hemlock is a member of the parsley family. It is often found along the edges of fields, pastures, roadsides and ditches. Poison Hemlock is an erect biennial plant that grows to a height of six feet or more and has many tiny, white flowers in umbrella-like clusters. Its stems are smooth and hollow with purple speckled spots. The purple spots are an important feature in identifying this plant. While it resembles Wild Carrot, it does not have the hairy leaves of Wild Carrot but has leaves that are hairless. It also has an unpleasant “mousy” odor.

Poison Hemlock is highly toxic and potentially fatal, especially to children who may mistake it for parsley, or its roots for carrots. It is toxic to humans and animals and is responsible for a number of fatalities throughout the northern United States and Canada.

Western Water Hemlock, Cicuta douglasii, is highly toxic and thought by some authorities to be the most toxic plant in the North Temperate Zone. It is in the same family as parsnip, carrot, celery and wild edible roots such as Wild Caraway or Yampah. It is a perennial that grows on damp ground and in shallow water.

Western Water Hemlock is an erect plant with a mature height of 3 to 7 feet and has leaves with many toothed segments. The leaf veins extend directly to the “V” between the teeth rather than to the tips of the leaves. Its large fleshy root is divided internally by cross partitions, which give it a very distinctive ladder appearance when cut open.

The entire plant is poisonous, especially the roots and rootstock. Children have been poisoned from using the hollow stems as peashooters or whistles. Plants of this species should be pulled, dried and burned. Livestock have been poisoned by ingesting plants that were pulled and dried, so burning is necessary to completely remove the plant material from the environment. Be sure to wear disposable gloves when handling this plant.

Western Water Hemlock and Poison Hemlock are just two of the 30 or more plants that can poison livestock. Livestock managers and landowners need to recognize plants that are potentially dangerous and be on the lookout for them to avoid the loss of valuable animals. For more information on poisonous plants, contact your extension office or the Poisonous Plant Research Laboratory, 1150 E 400N, Logan, Utah 84341.

The Poisonous Plant Research Laboratory is a part of the United States Department of Agriculture and is near Utah State University in Logan. There are smartphone apps now available that can help in identifying poisonous plants.