Australia's rarest eucalypt, the Mongarlowe mallee, survives with only six wild plants

Gum trees are synonymous with Australia, but only a handful of people have ever seen the Eucalyptus recurva.

Known as the Mongarlowe mallee or ice-age gum, only six plants have been discovered in the wild, just south of Canberra.

"When it was first found, it was a real botanical curiosity," said Genevieve Wright, a senior threatened species officer with the NSW Saving Our Species program.

Their age, based on the growth of the woody lignotuber of the largest specimen, is estimated to be between 3,000 and 6,000 years old.

Remnant of the ice age

Peter Bredell is a senior conservation horticulturist at the Australian National Botanic Gardens (ANBG) in Canberra and said his first reaction when he saw the gum was "that's not a eucalypt".

But he said the tree was probably Australia's rarest and most threatened eucalypt.

"We think that it's really the last six of an ancient, remnant species that was around back in the ice age," Mr Bredell said.

'No future' without intervention

Reproducing the tree has been a collaborative and coordinated effort between a team of ecologists and horticulturalists.

"There are no wild seeds," Mr Bredell said.

Over decades, the teams have worked together and have successfully cloned the trees by grafting wild cuttings onto hybrid Eucalyptus recurva rootstock in the nursery at the ANBG.

"The result is that we now have multiple copies of four of the six wild plants safely here as an insurance population," Mr Bredell said.

Tree can take decades to flower

To conserve the species, conservationists must get the flowers to bloom, pollinate, fruit and produce genetically pure, viable seeds.

Flowering is fickle in this species and can take up to 20 years.

"You can have one individual flowering in one year instead of all six. So, it's very hard to get the timing right," Ms Wright said.

The ANBG is trialling a growth regulator to try to help the gums flower sooner. But even then, keeping the genetics true means being a gatekeeper to pollinators.

"We're going to have to make sure that no pollinating insects get to the flowers because they'll bring pollen from other eucalypts that will cause hybrids," Mr Bredell said.

Delivering this project will take decades of dedication, but the team has put down roots and is sticking with it.