Twenty years ago this month, the Wollemi Pine made headlines around the world when it was discovered in a remote canyon in the Blue Mountains, west of Sydney.

Dubbed "a living fossil", the distinctive pines captured the world's attention because it was thought they had been extinct for at least 60 million years.

The Wollemi Pines, which were discovered in 1994, are about 40 metres tall and are hundreds, if not thousands, of years old.

Their trunks are more than a metre in diameter and they have distinctive bark which resembles bubbling chocolate.

But the last two decades have taken their toll on the prehistoric pine and its future is now under threat from a soil-borne pathogen called Phytophthora, which most likely walked in on the boots of uninvited visitors.

David Crust from the National Parks and Wildlife Service has been managing the original site and said the introduction of Phytophthora caused root rot in several of the pines.

The insurance population sits at the bottom of this remote valley. ( ABC News:Jessica Kidd )

"It has impacted on a number of plants and it has caused part of those plants to die back," he said.

"Obviously we're really concerned the Phytophthora could spread throughout the population and start to kill individual plants."

To ensure the species survives, an insurance population of young Wollemi Pines has been planted at another secret location in the Blue Mountains.

Mr Crust said the insurance site has been specially chosen for its similarity with the original site.

"That's obviously important from a scientific point of view in replicating what happens in the wild populations," he said.

Access to the insurance site is strictly controlled and each piece of equipment taken in has to be washed down with fungicide to stop the spread of Phytophthora.

Around a hundred saplings grown from cuttings taken from the original pines have been planted in a variety if sunny and shady locations at the site.

Research scientist Cathy Offord said the growth rate of the saplings have been compared to assess how the plant grows best in the wild.

"In this experiment we're finding that the higher light is giving the plants an advantage and they're growing better than plants in lower light," she said.

The location of each tree is recorded using GPS and they are regularly measured to track their progress.

Environment Minister Rob Stokes (far left) has listed the Wollemi Pine as the state's fifth iconic species. ( ABC News: Jessica Kidd )

New South Wales Environment Minister Rob Stokes marked the 20th anniversary of the Wollemi Pine's discovery by listing it as the state's fifth iconic species, alongside the koala and the brush-tail rock wallaby.

The Government also announced an extra $25,000 in funding from the Saving our Species program to protect the Wollemi Pine.

"It sends a very clear message that the NSW Government wants to ensure that this species has a solid and permanent future," he said.

"When you find a living fossil that has the same genetic make-up as fossils found that are 200 million years old, you know you have something very, very special to hang on to."

But in order to hang on to this remarkable plant, there is a simple rule: do not try to find it.

The locations of the insurance population and the wild population are top secret and they need to stay that way if the species is to survive.