11 minute read
Feature Article
On the trail of Australia’s rarest Macadamia species
Toby Golson, Senior Horticulturalist, Australian National Botanic Gardens, Canberra, ACT
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M. jansenii ripe fruit. Credit: Ian McConachie.
Background
Since 2000, Toby Golson has been the horticulturalist responsible for the in-ground rainforest collection at the Australian National Botanic Gardens (ANBG) in Canberra. One of the species in his care is Macadamia jansenii. In 2019 he received a BGANZ professional development award, enabling him to visit wild populations of M. jansenii and to meet others working hard to conserve this threatened species.
All four species of the endemic Australian genus Macadamia are threatened. They are restricted to lowland subtropical rainforest, from near Lismore in northern New South Wales to Bulburin National Park in south-east Queensland. Approximately 80% of this vegetation type has been cleared since European colonisation. Macadamia integrifolia is Australia’s best known and most commercially important indigenous bush tucker species. It has been growing at the ANBG since the 1970s, with the oldest trees flowering and fruiting regularly. Two of the three other species are also doing well in Canberra’s unfriendly climes: Macadamia ternifolia and Macadamia tetraphylla. M. tetraphylla is also an extensively grown commercial tree crop, as a hybrid with M. integrifolia. In December 2016, the head of the Landcare nursery at Gin Gin near Bundaberg, Ray Johnson, visited the gardens and kindly donated two plants of the fourth species, M. jansenii – the most recently described and rarest Macadamia species.
M. jansenii was first made known to Western botany in 1984, when native plant enthusiasts Ray Jansen and Keith Sarnadsky were walking in Bulburin National Park, inland from Bundaberg in Queensland. They recognised a fallen fruit as similar to, though much smaller than, a commercial macadamia nut. After an initial misdetermination at Queensland Herbarium, the species was formally described as M. jansenii in 1991. At the time it was restricted to one precarious population of fewer than 50 known individuals. Its rarity was immediately recognised, and it was listed as Endangered under both the Environment Protection and Biodiversity Conservation Act 1999 (Commonwealth) and the Nature Conservation Act 1992 (Queensland). Genetic analysis was undertaken, and an ex situ gene bank collection was propagated and later conserved at Tondoon Botanic Gardens, Gladstone. In 2017, the Commonwealth Threatened Species Commissioner included M. jansenii among 30 species in need of critical conservation intervention. This provided funding for a range of measures, including the establishment of five genetically representative replicate conservation collections at ex situ sites. The first 21 plants arrived at the ANBG in December 2020 and were planted in a prominent position in the rainforest gully. In 2021 M. jansenii was reassessed under the Nature Conservation Act and its status raised to Critically Endangered.
The Queensland trip
Travel restrictions delayed my Queensland trip until August 2022. My first destination was Tondoon Botanic Gardens where I renewed my friendship with curator Brent Braddick. I first met Brent at a BGANZ congress in Mackay in 2009. This led to an ongoing collaboration and transfer of regionally endemic species to the ANBG. This beautiful garden highlights the surrounding Port Curtis local flora and the extensive planting of M. jansenii adds significantly to its horticultural, scientific and conservation value.
After a wonderful evening in the warm hospitality of Brent and Rayleen at Miriam Vale, Brent and I travelled south to Bulburin National Park the next morning to meet Ray Johnson, Keith Sarnadsky and local ecologist Peter Moonie. Like most of the Australian east coast, the park experienced a savage, extended drought in the years up to 2019. This was followed by fires that burned right into its heart, but which fortunately spared almost all the known M. jansenii. While also precipitating extensive flooding, consistent rainfall since then has enabled widespread recovery of the rainforest. Sadly, this has been accompanied by ever-increasing infestations of Cat’s Claw Creeper Dolichandra unguis-cati and Caesalpinia spp. We spent a full and satisfying, sunny and cool ‘winter’ day walking into three of the four sub-populations found by Keith and Ray. A thorough survey in 2020, with researchers from Dr Alison Shapcott’s team at University of the Sunshine Coast, recorded 200 plants in total, although nearly half of those were too young to reproduce. All but a couple of individuals exhibited a multi-stemmed coppice-growth form, more shrub than tree-like, which reflects a history of fire and/or physical disturbance.
The few tall single-stemmed specimens were no more than 8 metres high; this is also the dominant form in cultivated specimens. Many individual plants were displaying young racemes of creamy pink flowers.
Brent kept up an informative and patient stream of answers to the myriad plant identification queries raised by his travelling companions and as the sun began to set over the western ridgelines, Keith sat us down at the very spot where he and Ray Jansen had recognised the distinctive shrub overhanging the creek 40 years previously. A natural raconteur, Keith told the story of their initial discovery of that first unusual nut through the long and winding path to formal description and recognition of a new species over a decade later. He and Ray Johnson have spent countless hours looking for further individuals and are still hopeful of locating more on the park’s rugged western side. For me, it was certainly an immeasurably rich experience to be blessed with the company of such an erudite and unaffected crew and the day was punctuated by laughter and good cheer in shared pursuit.
M. jansenii recovering from 2019 fires.
Credit: Ian McConachie.
Ray and I farewelled the others and drove into Gin Gin where, after one of those sound night’s sleep contented exhaustion brings, the next morning I visited the local Landcare nursery that Ray has husbanded for the last 10 years. A vast army of volunteers was working on propagation activities, raking paths in the adjunct botanic garden, potting and weeding nursery benches and attending to customers. Concentrating on the endemic flora of the surrounding area, as well as subtropical and tropical fruit plants, the nursery is a thriving community resource, which he marshals with considerable energy and patience.
We then visited a property between Gin Gin and Bundaberg which belongs to Jo and Russell Marsh. They have dedicated themselves to preserving the remnant dry rainforest patches that dominate their block on the edge of the Burnett River flood plain. This has led to them voluntarily supplying seed from the property to Landcare’s nursery and these local, hardy species becoming readily available to the local community, and indeed wider afield. I spent a couple of hours madly stuffing cuttings and seeds into bags and marvelling at their hard work and determination to do the right thing by the bush. The ANBG was fortunate to have the avid south-eastern Queensland environmentalist and botanist, Lloyd Bird, donate hundreds of collections of dry rainforest-propagating material to us from the 1970s to the 1990s. We know that most of these species, which are the same as, or very similar to, Jo and Russell’s, grow well, if slowly, in Canberra’s difficult climate, suffering droughts and −10 °C temperatures with remarkable resilience.
Ian and Jan McConachie at front and Ray Jansen between them in Mac country Bulburin NP 1992.
Credit: Ian McConachie.
Toby inspecting a profusely flowering specimen of Macadamia ternifolia on the road between Gympie and Cedar Pocket.
Credit: Ian McConachie.
We then swung by Bundaberg Botanic Gardens to visit some of the oldest cultivated plantings of M. jansenii. Later, at Childers we saw several extremely rare and stunning Isis Tamarinds Alectryon ramiflorus, both in the wild and cultivated, as well as one of the oldest cultivated M. jansenii growing and flowering beautifully, like its wild cousins, in a garden in the town. I then drove down the Bruce Highway to Gympie, where I processed the day’s collections.
The following day I enjoyed a full morning traversing a regenerating ex-soldier settlement block at Cedar Pocket east of Gympie. Since purchasing it in the 1970s, ex-forester Bob Whitworth has transformed an almost bare former dairy farm into a lush patch of subtropical rainforest dominated by towering Hoop Pines Araucaria cunninghamii. He has also been a kind and generous donor of plant material to the ANBG over the last 25 years. This arrangement harks back to John Wrigley’s time as the first curator of the Living Collections at the ANBG from 1967 to 1981. During this time, a whole swag of native plant enthusiasts, like Lloyd Bird, Society for Growing Australian Plants members and study groups from around the country would send seeds and cuttings to Canberra to assist in building up the country’s largest collection of wild-accessioned, cultivated, Indigenous plants.
Bob Whitworth’s Gympie property before his regeneration work began in the mid-1970s.
Credit: Bob Whitworth.
The same property today.
Credit: Bob Whitworth.
After lunch on the hoof, I met up with Ian McConachie of the Macadamia Conservation Trust (MCT), an organisation set up to conserve Australia’s wild macadamia trees in their native habitat, whose trustee is the peak body for the macadamia industry, the Australian Macadamia Society. Ian showed me several wild M. integrifolia and M. ternifolia trees in the Mary Valley before we went on to look at the newly opened Walk with Wild Macadamia track in Amamoor State Forest, set up in collaboration with Queensland’s National Parks and Wildlife Service. Ian is a veteran of 60 years in the industry as a grower and more recently as an avid conservationist and author of an upcoming definitive history of the macadamia story. He also played a major role in ensuring the establishment of ex situ conservation collections of M. jansenii, which is what had first brought us together, initially through correspondence in 2015, before meeting in person in Canberra in 2017. We shared a wonderful dinner that night with Ian’s wife, Jan, before I crawled into bed once again blissfully spent from the day’s activities.
Back at the ANBG
While I was away, 17 M. jansenii plants arrived at the ANBG – the second tranche of plants from Tondoon Botanic Gardens. These were kindly delivered by Denise Bond’s husband and daughter on their way through Canberra – couldn’t ask for better service than that! Denise is MCT’s executive officer and has played the pivotal role in seeing the M. jansenii ex situ project through. The plants will go into the ground with the warmer weather, and I have a much clearer picture of their cultivation requirements, form and stature thanks to my trip.
Acknowledgments
There are many people I would like to commend for the opportunity to undertake my visit to Bulburin and beyond. First, I would like to thank BGANZ for awarding me the professional development award. This is but one of the many ways it assists hands-on horticulturalists to further their careers, and I would urge practitioners out there to take up the challenge. It complements the immense networking possibilities provided by the biennial BGANZ congresses as well as the various virtual networks and state groups that sit under its auspices. Secondly, I would like to thank the Australian National Botanic Gardens, who supported me in the endeavour. Thirdly, and equally importantly, I would like to thank the many people who gave generously and wholeheartedly of their time, knowledge and immense good cheer. To Brent, Tondoon Botanic Gardens will indeed miss your drive and enthusiasm when you reluctantly holster your secateurs for the last time, but the garden you have been so instrumental in establishing is indeed a lush oasis. To Keith, may your wanderings around Bulburin find you more M. jansenii. To Ray, Gin Gin’s community is fortunate indeed to have you firing up their passion to grow and preserve their remarkable local flora, as is so evident in your collaboration with Jo and Russell. To Bob, your decision to forsake commercial forestry and dedicate your life to revegetating your block is inspirational. And to Ian, although we Australians often look offshore for validation, the macadamia story and your role in it should serve as a timely reminder of the richness of our indigenous plant heritage – may we treasure and value it as we ought.
