20 of the World's Deadliest Plants

Cerbera odollam (aka The Suicide Tree)
This species of tree belongs to the same family as Oleander, and is also quite toxic to humans. The seeds of the Suicide Tree contain a toxin called cerberin, a potent compound capable of disrupting calcium ion channels in heart muscle, which can lead to an irregular heart beat that is often fatal if the toxin is ingested in high enough quantities.