Synonyms for Ragwort (same or very similar meaning)
WordNet sense 1 (widespread European weed having yellow daisylike flowers; sometimes an obnoxious weed and toxic to cattle if consumed in quantity):
ragweed, benweed, Senecio jacobaea, tansy ragwortWordNet sense 2 (American ragwort with yellow flowers):
butterweed, Senecio glabellusFrom the ODE community, based on WordNetadd/edit