Returning hundreds of endangered Hairy geebung plants back into the Sydney wild

Discover how scientists have propagated hundreds of endangered Hairy geebung plants and restored them in native habitats in Sydney to help save them from extinction.

The endangered Persoonia hirsuta, known commonly as Hairy geebung, is a sprawling shrub with distinct yellow flowers that grows in patches across the Sydney region and typically blooms in summer.

Thousands of these plants used to make their home within dry sclerophyll woodlands, which are dominated by eucalypts and/or trees with small leathery leaves, but the species has gradually died off over the past two decades due to land clearing and other factors.

The small numbers of surviving plants paint a grim picture - it is estimated most current plant populations in Sydney consist of less than 10 individual specimens, which are scattered in groups across the metropolitan. 

Saving this humble Australian plant from extinction has been a passion for Dr Nathan Emery, a Restoration Biology Officer from the Australian Institute of Botanical Science, who is based at the Australian Botanic Garden Mount Annan.

And the research efforts of Dr Emery and the team of horticulturalists at the Institute have been rewarded. The team used important information from restoration trials in 2014 at NSW mining sites to recently translocate the plant to wider parts of Sydney. 

Passing on research success to wider Sydney

In November this year, the team provided 100 plants to Campbelltown City Council and worked with the Kentlyn Bushcare group, in south-west Sydney, providing conservation, propagation and translocation advice for the Persoonia species in local bushland.

The plants will also provide a key food resource for local wildlife, such as birds, kangaroos and wallabies, across different local ecosystems.

Dr Emery said data collected from the program will be used to help with the management and propagation of other small or declining populations of Hairy geebung across Sydney.

To assist with the conservation efforts, a small seed collection of the Persoonia is now stored at the Australian PlantBank, which is the home of plant conservation research, germplasm collection and storage in New South Wales, located at the Australian Botanic Garden Mount Annan. A number of plants also exist in the Living Collection on site at the Garden.

Urban expansion puts species under threat

As larger tracts of Sydney land have been cleared to pave the way for more homes, this threatened species has become increasingly isolated by large areas of urban development.

Dr Emery said many plants are exhibiting dieback symptoms, in which the plant begins to die from the tip of its leaves or roots backwards, owing to disease or an unfavourable environment, and researchers are still trying to determine the causes.

Key threats identified so far include possible inbreeding, land clearing, urban development, climate change and inappropriate fire regime. The 2019-20 Black Summer bushfires also caused major devastation killing many of the adult plants.

A hard nut to crack

The Institute’s long-term research into restoring this plant back into the wild began in 2014 thanks to funding by the Australian Coal Industry's Research Program (ACARP) with the aim to reintroduce the species back into the landscape at mine sites.

The research program resulted in scientists at the Institute being able to discover new populations of Persoonia hirsuta which led to the collection of enough seeds and vegetative material to determine how best to propagate the species.

However, the team’s effort in growing the plants was not an overnight success and it took time and patience due to a lack of viable seeds for collection from wild plants. 

Seeds of Persoonia species have complex dormancy mechanisms that must be overcome before germination can occur.

Initially, the seeds are protected by a hard, woody endocarp that must suitably weaken over time so the germinating seed can break through. Once the endocarp is weakened, the seeds themselves are physiologically dormant, requiring specific temperatures to stimulate the germination process.

At the Australian PlantBank at the Australian Botanic Garden Mount Annan, scientists physically removed the endocarp by cracking it in a vice, however the germination process was still impacted by the growth of microbes from within some seeds.

Propagation from vegetative cuttings was another option, but this process was labour and time intensive, requiring up to 12 months for the root to strike. The success of this method varied among vegetative material collected from different populations and genotypes.