Noxious Weeds to Watch Out For

Many weeds are poisonous to livestock. In most cases, livestock poisoning from plants occurs when there is little else to eat in the pasture (due to overgrazing and poor management), or the hay you are using contains toxic plants.

The Central Washington Animal Agriculture Team has a great fact sheet called “Selected Poisonous Plants of the Pacific Northwest” (#1007-2005) available at

A few common weeds to watch for in the Northwest include Tansy Ragwort, Bracken Fern, Buttercup and Common Groundsel. It is important to note that these are not very palatable to livestock. Poisoning usually occurs when the plants are mixed with hay, or when an animal is turned out in a pasture with very little else to eat. The best way to prevent poisoning livestock is to keep pastures well managed (to prevent weed issues) and to use good quality forage.

[toggle title=”Tansy Ragwort”] contains a liver toxin. Signs of poisoning can appear months after the plant was ingested. Symptoms include lethargy, poor appetite, weakness, nervousness, colic, aimless wandering, blindness, abdominal distension, incoordination, jaundice, coma and death from liver failure. [/toggle]

[toggle title=”Bracken Fern”]causes thiamin deficiency in single-stomach animals like pigs and horses. Signs of poisoning include weakness, depression, muscle tremors, incoordination, decreased heart rate, poor appetite and weight loss, and convulsions. In ruminants like cattle and sheep, Bracken Fern suppresses bone marrow activity. Symptoms include a marked fever, bloody urine and hemorrhage from multiple orifices.[/toggle]

[toggle title=”Buttercup”]is toxic when consumed fresh, but not when dry. Signs of poisoning include drooling, nasal discharge, diarrhea, colic, depression or excitation, labored respiration, a wobbly gait and sometimes blindness. Buttercup also contains a chemical that causes blistering and inflammation of tissues.[/toggle]

[toggle title=”Common Groundsel”]is in the same family as Tansy Ragwort and also contains a liver toxin. Signs of poisoning are similar to those caused by Tansy Ragwort. Livestock poisoning from Common Groundsel is most common when it is consumed with hay. Check hay carefully for the seed heads, which will be little white puffballs (similar to dandelions).[/toggle]


Noxious Weed Resources

Snohomish County Noxious Weed Control Board
Call 360-435-7830 or visit the website:

Washington State Noxious Weed Control Board
Visit the website: