It was the botanical equivalent of finding dinosaurs alive – but now the Wollemi pine faces a new threat to its fragile existence.
In 1994 the world was stunned when David Noble, a park ranger on a holiday hike, stumbled upon a living population of conifers that before then had been seen only as fossils.
Botanists at the Royal Botanic Garden, including Cathy Offord, realised the plant was one thought long-extinct with a presence in the fossil record going back 90 millon years.
The Wollemi pine was reborn.
Now those trees hidden deep in the Blue Mountains are under threat. One of the four stands of Wollemi pine has developed a fungal disease, likely from unauthorised hikers carrying in the Phytophthora mould.
"It would only take one extreme event to push them to extinction," said Heidi Zimmer, a research biologist who has just completed her PhD at the University of Melbourne on the Wollemi pine.
The ancient population of Wollemis is also missing middle-aged trees, which is concerning the botanists.
"It's like getting to a community and there are a lot of retirees and toddlers," Dr Zimmer said.
So in secret, Dr Zimmer, Dr Offord and their colleagues in 2012 planted a grove of trees in a second location to see how well the species coped with being moved in a process botanists call translocation.
Fairfax Media was given the first access to the secret Blue Mountains site to see the young trees thriving on a steep rainforest canyon near a pristine mountain creek.
As a precaution we were sprayed on our "boots, bags, bums and backs" with a methylated spirit mixture to protect the plants from infection.
Dr Offord is passionate about the survival of the conifers. "To see the trees growing here in the rainforest is almost as exciting as the first time I saw them growing in the wild. There is hope for a species that had almost disappeared from the planet," she said.
When Dr Offord was identifying the Wollemi two decades ago, Heidi Zimmer was nine years old at St Joseph's Primary School in Orbost, Victoria. When she heard about the "dinosaur trees", they gripped her imagination and didn't let go.
But given we can grow the trees in our gardens, why save them in the wild?
"It's not the same as having a wild population," Dr Zimmer said. "You wouldn't be happy just having pandas or whales in captivity. Ecological diversity is as important in the plant world as it is for animals.
"Humans have been responsible for so many extinctions. If we have it in our power to save a species, why shouldn't we?"
She and her team planted 191 trees at 30 sites with varying degrees of light and moisture. Of those, 29 have died, most of these due to infection from Botryosphaeria fungi. These were mostly in damper and darker locations.
Most of the others are thriving, giving botanists valuable information about the best conditions for them to grow.
"They're doing much better in the higher-light sites," Dr Zimmer said.
Dr Zimmer recommends future translocations should happen at sites with good light availability under protective tree canopy. She also recommends planting seedlings in future, "to account for the possibility that previously undetected genetic variation may emerge from seeds."
Dr Offord said that with the lessons learned from the experimental site, the next step will be to establish bigger populations in national parks.
She said: "Low genetic diversity might mean Wollemi pines will be less able to evolve in response to change, such as environmental change or exposure to disease. For example, we know the Wollemi pine is particularly susceptible to high temperatures.
"To help the Wollemi pine in the face of predicted climate change, we will select cooler translocation sites – sites which are predicted to remain within the Wollemi pine's known temperature tolerance range [between -10 and 35 degrees] for the next 100 years."
