Pamela Lillian Isley was a well-known and highly successful botanist. After learning she has a hyperactive immune system that causes her body reject any infection, poison, or outside contamination, she dons the guise of "Poison Ivy" and begins a career of crime. Those who spurn or commit acts that harm plant life or the environment become the object of the evil affections of Poison Ivy. She is evil yet can be incredibly seductive in luring men to do her bidding. Her crimes are often targeted toward wealthy men. She is known to use poison perfumes and lipstick as well as plant creatures of her own design. The animated series introduces Poison Ivy as a botanist who works for a cosmetics company developing new fragrances. When she sees then DA Harvey Dent destroy an endangered plant during the ground-breaking ceremony for Stone Gate Prison, he becomes the first object of her evil affections. After almost killing Dent with her poisonous lipstick, she is apprehended by Batman. This incident with Dent causes a great rift between Ivy and Two Face, who has a great animosity toward her. She is known to have an occasional partnership/friendship with Harley Quinn. She is not liked by the various members of the rogues gallery, but is greatly respected.

Mainstream: The seeds of Pamela Isley's madness were sown under the tutelage of Jason Woodrue, aka the Floronic Man. An unwilling experiment in plant/animal hybridization, Woodrue transformed Isley into a beautiful creature whose veins pumped toxins, while her skins exuded pheromones that quite literally drove men wild. To support her own botanical lifestyle, Isley began a life of crime, gravitating to Gotham City and an obsession with the Batman. Finding herself far too often incarcerated among Gotham's lunatic fringe in Arkham Asylum, Ivy escaped and secreted herself on a barren Caribbean island, which she transformed into a lush, verdant paradise all her own. Unforunately, her secret garden was destoryed by mercenaries, which led Ivy on a trial of vengeance back to Gotham and Arkham. She met Harley Quinn when the two were each doing their seperate heists at Gotham State Museum. Since then, they have created a very close friendship.