A self-described "tree detective" has discovered what he believes is a century-old endangered Queensland tree in a Bundaberg backyard.

The tree, believed to be a Planchonella eerwah, also known as the shiny-leaved condoo, black plum or wild apple, is named after Mt Eerwah, near Eumundi on the Sunshine Coast.

Bundaberg and District Landcare president Mike Johnson found the tree while doing a survey of the Bundaberg area using old plant listings.

He noticed the tree on a private property and left a note in the landholder's letterbox asking for permission to examine the tree more closely.

Mr Johnson said at first he thought the tree was an exotic, because of its unusually glossy leaves.

"That's what might have protected it from being cut down previously, because it's a pretty tree and so close to the house here," Mr Johnson said.

He estimated the tree could be 100 years old.

"It is exciting. It's never been found in Bundaberg before, but we have heard of one other tree being found further north in Townsville.

"So much of our environment has been destroyed, so [finding the tree] is like putting pieces of a jigsaw back together again."

The tree bears purple-to-black oval fruit and its common names include shiny-leaved condoo, black plum or wild apple. ( Facebook: Bundaberg Landcare )

The Planchonella eerwah is listed as endangered under the Commonwealth's Endangered Species Protection Act as well as Queensland's Nature Conservation Act.

The tree can grow to 40 metres, has glossy leaves and bears a plum-like fruit.

Only 160 wild Planchonella eerwah trees have been officially recorded in three areas of south-east Queensland: in the Ipswich-Beaudesert and Beenleigh–Ormeau–Pimpama areas and the Eumundi-Maleny area of the Sunshine Coast.

The tree was thought to be extinct until its re-discovery in 1980, however it remained threatened by land clearing, weed invasion and pests such as feral pigs.

The tree will be cultivated by the local Landcare group. ( Facebook: Bundaberg Landcare )

Mr Johnson said the Bundaberg tree had been informally identified as a Planchonella eerwah by respected amateur botanist Glenn Leiper, and a sample of the tree would be sent to the Queensland Herbarium for a formal identification.

Mr Leiper said the tree's presence in Bundaberg could indicate it was a remnant of an older rainforest, and part of a continuous population of the plant dating back thousands of years.

"Climatic change and fires would have wiped out the rest, which is why we are only seeing little pockets of the population now," he said.

"It's a plant that may have been spread by ancient cassowaries, because the seeds are too heavy and large for smaller birds to digest."

More trees of this type may be out there

Mr Leiper said the discovery of the tree in the Bundaberg region was significant, and could open the possibility that this tree was a new genotype.

"We could find more of these trees," he said.

"If this species has been found, it could also mean there are more remnant species to be discovered. This is why it is so important to keep these remnants intact."

The landowner on whose property the Planchonella eerwah was found has vowed to protect the tree and was keeping his name and address private.

"It's like finding you've been left in charge of an endangered animal or an orphan child," he told the ABC.

"We feel like we've been given the task of seeing that it survives and thrives."

The seeds of an endangered tree which is endemic to south-east Queensland. ( Facebook: Bundaberg Landcare )

Mr Johnson was now seeking property owners with dry rainforest in the Bundaberg area to grow more of the Planchonella eerwah.

The Bundaberg tree is fruiting and could potentially be used to propagate hundreds of new seedlings.