Tansy ragwort is a noxious weed that is commonly found in pastures, meadows, and along roadsides. This weed is native to Europe and has a bright yellow flower that blooms in the summer. There are several synonyms for tansy ragwort, including Senecio jacobaea, Stinking willie, and Common groundsel. These synonyms all refer to the same plant species, which is considered a toxic plant to livestock. Tansy ragwort has been known to cause liver damage to animals that consume it, so it's important to control its spread and remove it from pastures and other areas where livestock graze.