Tansy ragwort is an invasive, toxic biennial weed from Europe often found in pastures and along roadsides. It makes horses sick and can kill them if they eat enough of it.
The plant is also toxic to cattle, sheep, some goat breeds and people. Even though animals tend to avoid it, they can eat enough of it inadvertently to get sick or even die. The biggest risk is when the plants have been cut down or are mixed in the hay because the plants are not as bitter then but still remain toxic.
Identifying tansy ragwort is not difficult and there are many photos below and on our website that can help you.
Tansy ragwort, called hierba de Santiago in Spanish and Senecio jacobaea in Latin, is commonly confused with a more widespread weed called common tansy, tanaceto or hierba lombriguera in Spanish and Tanacetum vulgare in Latin. Common tansy is also a European species and somewhat toxic, but it is not usually consumed by livestock due to its strong odor and bitter flavor. The two “tansies” are most easily distinguished by their flowers. Tansy ragwort flowers have 13 external ray petals and common tansy has button-like flowers with no external ray petals.
Dig out plants with a shovel or pull out the plant, complete with roots. If there are flowers, cut off the top and bag it up for disposal in the garbage.
If you have a large infestation, we can give you advice on the best method for the site. The most important thing is to stop the plants from going to seed so you can prevent the plants from spreading more. Read more about controlling tansy ragwort here: in English or en español.
Keep animals out of infested pastures. They will try to avoid eating tansy ragwort, but it is better to be safe than sorry. Try to keep your pasture free of toxic plants like tansy ragwort by keeping it healthy and watching for the plant throughout the year.
Please tell us about any tansy ragwort you see in King County. You can call or email our program or simply report it online on our website. Tansy ragwort is a regulated noxious weed in King County and everyone is required to control it, including the government. Please help us find it so we can make sure it gets controlled.
If you have any questions, please contact us. Thank you for helping us stop the spread of this dangerous noxious weed!
Thank you for the article. I will give it to folks in my community that are unaware of how to manage these noxious weeds.
Horses will not eat living ragwort unless they are starved, the only real danger is if it gets into hay. Provided they have other grazing as well, sheep will not be harmed by eating ragwort.
Thanks for the helpful information. I agree that horses won’t eat living tansy ragwort when they have plenty of healthy food. I am always sad when I see situations where they do eat it, because that likely means there is little else for them to eat. Also, I used to teach that tansy ragwort couldn’t hurt sheep, but I was informed by a sheep farmer that it does hurt them if they eat enough, which they do sometimes, so I’ve stopped saying it is harmless to sheep. As you point out, it is all about giving your animals healthy food so they won’t be forced to eat plants like tansy ragwort. I believe a healthy pasture and quality hay is the best strategy!
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