King's Holly, otherwise known as Lomatia tasmanica, is believed to be at least 43,000 years old.

Only one cluster of the ancient plant remains in a secret southern Tasmanian location, surrounded by deadly root rot.

Tasmanian explorer, Denny King, discovered the plant in 1937.

It's believed there are fewer than 500 plants in the small secret location.

Greg Jordan, from the University of Tasmania, said King's Holly is probably the oldest living plant in the world.

"Definitely to date it's probably the best candidate for the oldest plant in the world," he said.

An intensive breeding program at Tasmania's Royal Botanical Gardens started in 2004.

The aim was to set up an insurance population of 50 plants in pots, but to date fewer than half have taken.

Mr Jordan said establishing an insurance population was a challenge.

"The King's Holly doesn't do sex," he said.

"That's because it has three sets of chromosomes instead of two."

The plant bears pink flowers but produces neither fruit nor seeds.

It only reproduces vegetatively, meaning a new plant only grows when a branch falls and develops its own roots establishing a separate, but genetically identical, plant.

Natalie Tapson, from Tasmania's Royal Botanical Gardens, has been working with King's Holly for around two decades.

In that time several different techniques of growing the plant have been tried, but all have had their setbacks.

Ms Tapson said that while cuttings generally took root, they were difficult to transfer to larger pots.

"One of the issues is you get this blackening off, so whenever you cut a stem it blackens and it dies, so it's very very touchy," she said.

King's Holly or King's Lomatia, was discovered by Tasmanian explorer, Denny King. ( Tasmanian Parks and Wildlife Service )

Ms Tapson now believes grafting King's Holly onto another plant could be the solution.

"By putting it on to a root stock, it's hoped that when you plant it out, or transfer it, you're not going to have that loss because the root stock is stronger," she said.

As well as root rot, scientists fear a fire could wipe the cluster out.

However, it's also feared a lack of fire could allow other plants to grow over the top of it.