The world's largest and smelliest flower has opened in a pong of glory in Sydney's Royal Botanic Gardens Thursday.

(The titan arum is flowering at Sydney Royal Botanic Gardens. Reuters photo)

The titan arum is a native of Indonesia and its botanical name, Amorphophallus titanum, means very large, deformed, penis.

It can grow up to three metres tall and has a banana-like, pale yellow wrinkled centre and a claret coloured frilly skirt.

Botanic Garden spokesman Dr Tim Entwisle says it smells like rotting flesh and today is the best day to see and smell it. People actually queue up to saviour its stench.

"We've only had this on display once before - the first time we'd ever had it two years ago, the only complaints I got was that it didn't smell bad enough," he said.

"It's a strange thing, particularly little kids love it and you can put it head close to it and it really does smell a bit off.

"That's what it does out in Indonesia where it grows, so it can attract these flies in to pollinate it."

Mr Entwisle says the flower has opened early this year because the tropical centre is warmer than normal.

He says it has nothing to do with global warming.

(Source: ABC Newsonline.au)