Mis-packaged Seeds

I have three raised flower beds that I have carefully been watering and killing any weeds that would come up for about 9 months now and finally the weeds stop germinating. I even would rough the soil up to make sure no seeds were under the surface and passed over. I purchased approximately 40 seed packs and proceeded to plant these beds. In the exact pattern that I planted Scarlet Flax Flower seed I got what I have identified as Yellow Menzies' Fiddleneck. I had never seen or heard of it before. I have a couple of questions. First has anyone else had the experience of planting something from a commercial seed package and something entirely different come up? This is the second time it has happened to me and they were differnt companies. Second is anyone familiar with this Menzies' Fiddleneck? I am going to start pulling them out because I read they are toxic but do you think they will continue to come up repeatedly. Should I clear the flower beds and de-weed they way I previously did for the 9 months? Thanks for any input.