Susan , the Dept. of Agriculture never came and visited my garden! :
Actually my sister, who lives in a suburb of Minneapolis, (zone 4) has had a very difficult time keeping them over. I think because we usually have such heavy snow cover for insulation is the only reason I can have them here.
They are poisonous if you eat stuff from them, they cause your heart to beat to fast which stops it. They do use it in heart medicine but they have tested it to know the amount that is beneficial not detrimental.
People have been growing it for centuries without a problem so I'm not gonna eat any part of it but I'm gonna keep growing them.