There are a lot of poisonous plants, but as far as I know, man is the only one stupid enough to eat them. Take milk weed. Poisonous and the only animals eating it are poisonous and display brilliant colors alerting prey that there is at least a belly ache associated with eating them. I saw on list that showed taro as poisonous, and have had it drape into my pond for at least 15 years, and haven't seen any dead koi, and do occasionally see them pull and tug on the leaves that fall into the pond. I don't know if it is the taste repels animals, or what the mechanism is but like bears in the woods, they know what to eat, and you don't see them falling out dead over the stuff they shouldn't eat.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard