Plants have developed an array of deadly defences and chemical compounds can turn an innocent looking ornamental into a deadly assassin. Different toxins affect different parts of our body too, causing everything from kidney failure, heart failure, brain damage and even death. It's why humans have used poisonous plants in weapons to kill prey and even commit murder. But most of the time, our run in with poisonous plants is a mistake with thousands of accidental poisoning illnesses and deaths each year all around the world because it's often very hard to tell the difference between something that's poisonous, and something that's not.