Auckland Domain manager David Millward said it was the first time the plant had produced a bloom, creating a good deal of excitement amongst his team and visitors to the garden.
"The titan arum, as it's commonly known, can produce a single leaf the size of a small tree every year for seven to 10 years before showing any signs of producing a flower," he said.
"We have been watching this one very closely and were delighted to finally confirm that a flower was on the way - it felt a bit like being expectant parents."
Mr Millward said he hoped many visitors were able to come and see the titan arum, as it may well be a once-in-a-lifetime opportunity.
"If it gets very busy, we may need to carefully manage entry to ensure everyone gets a chance to move through the glasshouse and we'll be reminding people that it's very warm and smelly inside."
Auckland Council parks, sports and recreation manager Ian Maxwell said it was a momentous occasion for the Wintergarden at for botany in New Zealand.
He said many New Zealanders would have seen the plant on David Attenborough's Kingdom of Plants documentary but never thought they might see one in Auckland.
"We are very proud to be joining places like the Royal Botanic Gardens of Kew and Melbourne in producing one of these flowers.''
The bulb of the titan arum produces a single leaf the size of a tree each year.
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For seven to 10 years it goes through a life-cycle of leaf, dieback and dormancy before a bloom may appear. Once the flower starts to emerge it can grow to more than 3m tall, at a rate of 10cm per day.
Both male and female flowers are produced in the same inflorescence - the female flowers open first, and the male a day or two later.
The flower is in the Wintergarden's tropical glasshouse, which maintains an average temperature of 28C.
