I'm writing a story set in the... older ages. I don't really know when it's supposed to be. I think about the renaissance. Anyway, in the story, the queen wants to poison a horse and its foal (because of a lot of drama and blah blah blah). I was wondering if there was some flower or something that she could feed the mare so it died, and it would poison the foal through the milk, but it would only grow ill. To make it more difficult, this is a pretty cold country, but it would probably be possible to get the flower from a warmer place.