In Tasmania however,Hardenbergia violacea is an uncommon, sprawling under shrub which is listed as endangered on the Tasmanian Threatened Species Protection Act 1995.
DNA research has identified that the Tasmanian form is genetically distinct from the more common mainland forms, perhaps even warranting description as a separate subspecies (Larcombe 2006). Tasmanian plants are less vigorous than cultivated mainland garden varieties tending to be more prostrate and the flower colour more intense.
The Tasmanian Hardenbergia is only known to occur in one area on the Pontos Hills near Hobart, growing on Triassic sandstone outcrops, at altitudes of 105 to 125 m above sea level. The population has a linear range of less than 400 m, scattered over an area of 1.8 ha.
One sub-population of approximately 44 individuals is on private land which has been placed under a conservation convenant. A second sub-population 1.7km to the south is now considered to be extinct.The main threats to this species in the wild are drought and browsing pressures. Fortunately theRoyal Tasmanian Botanical Gardens (RTBG) managed to secure 7 genotypes from the southern population prior to its extinction which were maintained at the RTBG as a “seed orchard” for seed production. Propagation material from a number of genotypes from the northern population were also collected and used as seed orchards.
The RTBG safeguards this species as a seed collection at its Tasmanian Seed Conservation Centre (TSCC)and at its partner institute the Millennium Seedbank at the Royal Botanic Gardens Kew, UK.During the 6 years from 2008-2014 the RTBG harvested a total of 17,770 seeds from the Hardenbergia seed orchards. Over 8,000 seeds were harvested from the extinct population genotypes and the opportunity to pollinate across the two subpopulations and harvest seed with a potentially broader genetic diversitywas also actioned, resulting in 6,000 seeds. A separate seed harvest of the northern population was also secured with 3,600 seeds harvested. These seed lots are stored separately and are being held for use by the Threatened Species Section (DPIPWE) in their recovery plan for this species and as an ex-situ conservation holding.
Building Resilience for the Future Stability of Hardenbergia violacea in Tasmania
In 2010 the Penna Landcare Group were awarded a Tasmanian Landcaring Grant from the Tasmanian Landcare Association to ‘Develop an in-situ sub-population of Hardenbergia violacea at Pontos Hills’ and volunteers from Threatened Plants Tasmania assisted staff from the Biodiversity Unit of DPIPWE, and the RTBG to augment the wild northern-most population. This augmentation involved the addition of 76 RTBG nursery grown plants to an unpopulated site on Pontos Hills.
As browsing by native animals was considered a major threat to the success of any plantings all the plants were enclosed within 3 rabbit and possum proof fenced areas. Working in difficult steep, rocky terrain, the hard-working team managed to complete the project in 2 days.
Mother Nature kindly provided a rain shower the day after planting to boost the manual watering the new plantings received. All three plantings are being monitored periodically to assess the success of this population augmentation program.
If successful, this project will have effectively doubled the population of native, Tasmanian Hardenbergia violacea in the wild and hopefully assist in protecting and building resilience within the population.
The RTBG acknowledges the generous assistance from the then Landowner, Tony Scherer; Rob Walker and the Penna Landcare Group; Anne Thwaites, Ken Wright, Oliver Strutt and Nell Hilliard from Threatened Plants Tasmania; and Mick Illowski, Oberon Carter and Richard Schahinger from DPIPWE, in completing this project.
Plans are now in place to fence an area for the re-introduction of genotypes from the extinct southern population once funding and the opportunity becomes available.If you would like to offer financial support for this project please contact Natalie Tapson –Natalie.Tapson@rtbg.tas.gov.au.