Strychnine tree

Famous as a rat poison, it has been implicated in all manner of terrible poisoning incidents. So, let's assume you'd want to stay away from any plant that shared its name. The seeds of the Strychnos nux-vomica tree, native to Southeast Asia, are the primary source of strychnine, which may be best known as a poison but was once used as a medicine (for its stimulant properties). Strychnos nux-vomica seeds are still sometimes prescribed in traditional Chinese medicine as a cancer treatment. With that said, you'll probably want to steer clear of strychnine: the severe convulsions that can eventually lead to death from exhaustion are probably reason enough. The fact that it's the primary ingredient in rat poison is probably a good reason, too.