Boosting a threatened mint bush in Tomaree
By Sue Olsson, Coordinator, Friends of Tomaree National Park
On World Environment Day, we celebrate the beauty, joy and natural treasures of our precious planet – but we also recommit to protecting and preserving them for generations to come (from UNEP speech 2024).
This year, on Wednesday June 5th 2024, a group from the Friends of Tomaree National Park celebrated with planting the threatened Villous Mintbush, Prostanthera densa, with a team from the NSW Government’s Saving Our Species program, SOS.
We planted nearly 60 young plants grown from the cuttings of wild plants under the expertise of the Hunter Region Botanic Gardens.
SOS has been working hard to help secure this species. Villous Mintbush is listed vulnerable, threatened with extinction in the wild, under both State of NSW and Commonwealth legislations.
Villous Mintbush — distinctive leaves and flowers
Prostanthera densa is an erect mint-smelling shrub that can grow up to 1-2m tall, though in the southern part of its range it is rarely more than 1 m tall.
Its branches and leaves are covered with long, spreading hairs. The leaves are usually in pairs and almost triangular in shape, extending to 15mm in length and 12mm wide. They are dark green above and paler below, with curled-under edges.
The tubular flowers grow in the angles where the leaves meet the stems. Flowers are pale mauve to mauve with white and orange markings in the throat.
Flowering occurs year round, possibly more in spring.
Just a few scattered coastal populations around NSW
Only known in NSW, Villous Mintbush extends from Nelson Bay to the Beecroft Peninsula, now at only a few select localities, and in the Currarong area of Jervis Bay.
The Sydney and Royal National Park populations were thought possibly extinct, but the species is now known to occur at several locations in this locality including Bass and Flinders Point in Cronulla, Royal National Park and Garawarra State Conservation Area.
<< Prostanthera densa known locations, from PlantNet
Urban development, throughout Villous Mintbush’s range, has been a major threat with the loss and fragmentation of habitat,. That’s been a past issue in Nelson Bay where the species and its habitat were cleared.
What conditions does the Villous Mintbush prefer?
Prostanthera densa generally grows in sclerophyll forest and shrubland on coastal headlands and near coastal ranges, chiefly on sandstone, and rocky slopes near the sea.
It is also known on the wooded flanks of volcanic peaks.
Plants regenerate from rootstock after fire and flower within the first year or two.
However, they are unlikely to withstand hot fires, and can be shaded out if no fires – inappropriate fire regimes have probably been a factor in their demise. Not a lot is understood yet about the appropriate fire regime.
Helping with recovery – establishing additional populations locally
One recovery strategy is to enhance existing populations, but on the Tomaree Peninsula, the only known populations were in two areas, each with very few plants, adjacent to urban development, and not secure. SOS decided it was not advisable to supplement those tiny populations – so took cuttings to grow new plants elsewhere.
While the mint-bush had been recorded in the past within Tomaree National Park, extensive search at those locations and surrounds was not successful – seemingly none remained.
In 2020 in Nelson Bay, the SOS program trialled two areas within Tomaree National Park, testing their suitability. One planting grew fairly well, and in May 2021 SOS extended that planting. The other 2020 planting mostly survived but hasn’t thrived.
Friends of Tomaree NP were fortunate to become involved with SOS program early in 2021. Michael Wood, SOS, showed us the 2020 planted sites, the typical terrain, the vegetation communities, the dappled light conditions and the ideal soil features. From there we looked for suitable sites.
May 2021 we planted our first 20 plants at our selected site. With late Autumn warmth, and ample follow-up rain, our plants thrived. The site we selected seemed ideal.
Networking brings new light to an old discovery
A benefit of the SOS Prostanthera densa program involving the Friends of Tomaree, was to create additional community links – an objective of the SOS program.
Within a week or two of being introduced to the SOS program in 2021, we were out looking for orchids and crossed orchid-paths with local naturalist, Philip Diemar (left). To our surprise, Philip knew of a significant natural population of the Villous Mintbush within the national park. And to the greater surprise of the SOS program leader, as this population was so remote within the park.
Such discoveries reinforce the importance of making connection between scientists and community in increasing mutual knowledge and understanding.
This population has now become a significant resource for cuttings for future plantings.
Fast forward to World Environment Day 2024, three years later
Seventeen of our original twenty 2021 plants are flourishing, an 85% success rate.
Most plants are 1-1.5m tall, and many were in flower. We were delighted. We all admired the vitality and beauty of these bushes..
Left, from left
Paul Shearston (Hunter Region Botanic Gardens)grew the plant stock from cuttings with phenomenal success,
Sue Olsson involved in planting 2021 and 2024,
and Aaron Mulcahy, NPWS project lead SOS program.
Below, Aaron Mulcahy, immediately to his right Melissa Mays, and far right Dee Ryder.
We consolidated our 2021 site with an additional 40 plants. And trialled another site with 20 plants.
Our World Environment Day plants were grown again at the Hunter Region Botanic Gardens (thanks Paul), and from the same plant population Philip Deimar had discovered. Philip’s discovery not only contributes to the understanding of Prostanthera densa in the wild, but has enabled an additional genetic stock for plant cuttings, important when establishing planted populations.
From little things, big things grow!
Top, Anita Crotty planting,
Centre, Christophe Tourenq watering and John Chapman
We wait keenly to see the outcomes.
A very enjoyable and meaningful morning
We all participated as we enjoy planting, enjoy the camaraderie, and enjoy contributing positively to our environment – especially strengthening threatened species populations.
We also enjoyed surprise wildlife — spotting a solitary Grey-headed Flying Fox (thanks Dee), some colourful coral fungi and an intriguing bootlace orchid.
And we enjoyed a delicious morning tea and more chat. Thank you NPWS & SOS!
What a lovely way to appreciate nature and celebrate World Environment Day – a win win all round.
As well as being World Environment Day, this was part of our program Celebrating 40 Years of Tomaree National Park | 2024.
Come and join us as we work to enhance the integrity of Tomaree National Park, read more at www.ecops.au/fotnp, or email tomaree-np-friends@npansw.org.au
Photos courtesy of Lucas Grenadier SOS, Sue Olsson
References
Department of Climate Change, Energy, the Environment and Water, Prostanthera densa Conservation Advice, July 2008. https://www.environment.gov.au/biodiversity/threatened/species/pubs/12233-conservation-advice.pdf
Friends of Tomaree National Park Kicking the milestones for Tomaree
Office of Environment and Heritage Fact Sheet Villous Mint-bush, January 2020. https://www.environment.nsw.gov.au/-/media/OEH/Corporate-Site/Documents/Animals-and-plants/Threatened-species/saving-our-species-factsheet-villous-mint-bush-200036.pdf
Office of Environment and Heritage Villous Mint-bush – profile, August 2023. https://threatenedspecies.bionet.nsw.gov.au/profile?id=10676
PlantNet, NSW Flora Online, Prostanthera densa, 1999. https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Prostanthera~densa