Also known as Bunga Bangkai, the Corpse Flower, or Amorphophallus Titanium
The titanarum is, by one definition, the world's largest flower. It is an Indonesian plant that blooms only rarely and unpredictably in its 40 year life, and emits an intense stench of rotting flesh for about eight hours of its 3 day bloom when it does so. There are only a few dozen of these endangered 6 foot plants in botanical centers, and when they bloom they attract quite a crowd both for the novelty and to experience the stench, which attracts the carrion-eating beetles which pollinate it.
Well, that depends on how you define "largest"