University folklore warns that any undergraduate who fails to study before the tree's first bloom appears will fail their exams.

For those who heed the warning and pass their degree the tree becomes the traditional backdrop for graduation photos.

"It's got to be one of the most famous trees in the city," said Craig Barker, who runs heritage tours of the university.

But the iconic tree is not immortal, and at 86 years old is showing its age. So beloved is the specimen that the university has gone to extreme lengths to ensure its legacy continues.

"Given its significance, and knowing it won't live forever, we hired a specialist jacaranda grower to take cuttings," said the university's landscape and grounds manager, Mark Moeller.

Grafted on to the base of other jacarandas, the cuttings produced two clones. Now young trees, the pair are being tended by central coast tree grower, Jim Warner, himself a University of Sydney arts/law graduate.

"There's a photo or two of me taken under that tree about 50 years ago," he said.

When it comes time to be removed, it will be replaced with genetically identical stock. With special care the tree could stand for another 30 to 40 years.

"When it's flowering, it is absolutely stunning. I don't the quadrangle would be the space it is without that tree," said Mr Moeller.

But the tree, a South American native, hasn't always been loved. It was planted in 1928 by a university academic, E G Waterhouse. It was the professor of comparative literature's third attempt to put a jacaranda in the quadrangle. Two previous plants had not survived.

Dr Barker said Professor Waterhouse was a keen horticulturalist, who popularised camellias in Sydney gardens, and took it upon himself to beautify the university. His vision was to have rows of jacarandas around the grounds. But in many places, including the quadrangle, the trees were ripped out.

Rumours suggest it was students playing pranks, but it was more likely to have been staff stealing them for their own backyards, said Dr Barker, the manager of the education and public programs at Sydney University Museums.

The current jacaranda was planted near the rooms where philosophy lessons were once taught, providing shade for the philosophers as they sat and contemplated the world around them.

Most years the tree blossoms in November, giving students the opportunity to commence their study after lessons have finished, but every so often the tree blooms in October, panicking superstitious students, Dr Barker said.

"This year it bloomed right on time, in the last week of lessons," he said.