widespread European weed having yellow daisylike flowers; sometimes an obnoxious weed and toxic to cattle if consumed in quantity

[ Syn: ragwort , tansy ragwort , benweed , senecio jacobaea ]

any of numerous chiefly North American weedy plants constituting the genus Ambrosia that produce highly allergenic pollen responsible for much hay fever and asthma

[ Syn: ambrosia , bitterweed ]