Inala Jurassic Garden: a global collection of Gondwanan flora on south Bruny Island, Tasmania

Dr Tonia Cochran, Owner, Curator and Collection Manager, Inala Jurassic Garden, South Bruny, Tasmania

The Inala Jurassic Garden is a privately owned botanic garden located on south Bruny Island off the south-eastern coast of Tasmania. Its relatively remote location on an ‘island off an island off an island’ is rather a fitting place for a garden which features representatives of living plant families whose ancestors thrived on the ancient Gondwana supercontinent when it began splitting apart in the Jurassic period to form today’s southern land masses – quite the Jurassic Park with its plant equivalents of dinosaurs that are still with us today! Unlike theeventual size of some of its plant inhabitants, the garden is currently quite small (around 5 acres,or 2 hectares, in size). However, it is located within my 1,500 acre (600 hectare) conservationcovenantedproperty ‘Inala’ which is predominantly comprised of natural vegetation: mostly wetsclerophyll Messmate Stringybark Eucalyptus obliqua forest with a mix of heathland, wetland and rainforest elements and a small balance of pasture which was created by the early European settlers in the mid-1800s (Fig. 1).

The concept for the garden is a culmination of ideas formed over more than 25 years of leading tours in Tasmania and across the globe and has been inspired by Tasmania’s Gondwanan connections. As the last piece of Gondwana to separate from the Antarctic continent around 45 million years ago, Tasmania is well placed to demonstrate this connection, both in terms of its native flora and its geology and is therefore an ideal base to showcase such a garden.

Tonia Cochran. Photo: Bronwen Scott.

Figure 1. Aerial view of the Inala property showing the location of the Inala Jurassic Garden. Photo: B. Moriarty.

Over this period, the Gondwanan theme frequently reoccurred, mostly during Tasmanian tours where Gondwanan floral relics such as Myrtle Beech Nothofagus cunninghamii, Sassafras Atherosperma moschatum and Leatherwood Eucryphia lucida abound in our cool temperate rainforests. These species are also present in other areas of Australia such as south-western and eastern Australia and several of the international destinations that we visit on tour such as South Africa, South America, Papua New Guinea and New Zealand, where Gondwanan flora feature prominently.

A series of incidents inspired the actual creation of the garden. In 2012, the Australian Government was offering funding on a dollar-for-dollar basis for ‘innovative tourism projects in regional areas.’ Around the same time, I met a plant collector who specialised in Gondwanan species, and I sold the last of the stud cattle herd that I had farmed for the previous 25 years. The natural progression (in my mind) was to plant a few specimens in a five acre area of pasture previously used as a cattle paddock to demonstrate the concept of Gondwana in terms of its flora so that we could use this as an educational tool, both on our tours and for access to the general public. On being advised of the success of the Commonwealth grant in 2013, landscaping began in earnest, with the addition of shallow lakes, huge locally sourced Jurassic dolerite boulders, concrete easy-access paths and topographical changes to the garden beds using local contractors and huge machinery (Fig. 2). Researching and collecting specimens was also reaching an obsessive level and an important decision had to be made regarding what constituted a Gondwanan taxon. My main interest was plant families of ancient lineage that occurred by vicariance − geographical separation because of plate tectonics and consequent speciation on the separate continents formed by the splitting apart of the Gondwanan supercontinent. But I also decided to include, for interest and comparison, those species of more geologically recent taxa with a Gondwanan distribution that may have occurred by past long-distance dispersal after the separation of the supercontinent.

Figure 2. Landscaping with local Jurassic dolerite rocks and constructing an easy access path. Photos: T. Cochran.

The time had also come to decide how the garden was to be planted. At first, the concept was to plant the species together within their respective continent of origin so that visitors could pass between separate garden beds containing Australian, New Zealand, New Caledonian, South African and South American plants. I quickly realised this wasn’t going to work, either from a plant management point of view, or in terms of demonstrating the concept as people moved between similar-looking beds. Planting specimens from different Gondwanan countries together in family groups seemed to solve both problems and the similarity between species was much more apparent by direct comparison. My theory was that species from the same family would probably require similar cultivation requirements. The paddock was therefore divided into sections where I thought (and hoped) that the different families would grow best, for example, water-loving members of the families Gunneraceae and Restionaceae were planted near the waterholes and waterlogged areas of the paddock, while members of the Proteaceae were planted in well-drained, sunny positions.

The first specimens were planted in October 2013. After planting, we heavily mulched with eucalyptus bark to provide good preliminary garden preparation which would reduce consequent weeding and watering. Each specimen was also labelled with the name of the family to which they belonged, their common and scientific name, their country of origin and a catalogue number specific to each species which also included the year it was planted. Within two weeks of installing the plant labels, we found that birds such as robins were irresistibly attracted to them as perches and consequently, they became quite heavily covered with guano. The addition of wire ‘poo deflectors’ which are higher than and pointing behind the label, has been a huge success (Fig. 3). A Microsoft Excel spreadsheet database was also developed containing further details on where and when the plants were sourced, cultivation notes and additional notes on the requirements of each species in their wild state, to be updated as required and kept on file for reference and further research.

The next major task was to keep the specimens alive and healthy. My previous experience with growing plants was a cactus collection when I was a child, some carnivorous plants and orchids in my office, and native Australian plant cultivation. This included a 5-acre commercial Brown Boronia Boronia megastigma plantation (comprised of around 35,000 plants) which was harvested annually for the essential oil industry for a period of over 15 years in the 1990s and 2000s. It was therefore a huge learning curve to suddenly determine the various requirements of hundreds of different specimens comprising over 50 plant families from around the world.

Figure 3. Plant label with ‘poo deflector’ which gives birds an alternative perch and keeps signs clean! Photo: T. Cochran.

In addition to extensive research on the natural conditions of each taxa in the wild, I extrapolated this information to soil types and fertility levels of each Gondwanan country. For example, I worked on the assumption that the New Zealand species would require more fertilizer because of the rich, volcanic soils of their native country, while Australian specimens were given small amounts of native fertiliser and products such as seaweed extract as required. This has largely been successful, and we try to learn from our relatively few failures (which we take to heart).

Watering was another issue that needed to be addressed. Because of the amount of mulch applied, the water requirement is much reduced and due to the individual needs of each plant we have elected not to water with sprinklers or any broad-range method, choosing instead to hand-water as required. For this we have designed a reticulated system with strategically placed taps around the garden for easy access. Rainwater is collected in four 22,500 litre tanks and additional water is periodically applied to the water-loving plants by soaking the whole area using a hose that is gravity fed from a larger waterhole into the shallow pools within the garden to keep them full over summer. As the garden has grown and root systems develop, the need to water has further reduced.

The garden opened to the public on 31 March 2014. In its early development, I must admit it looked much more like a cemetery than a garden with its new landscaping of huge Jurassic dolerite rocks which were sourced locally on Bruny Island and plant labels which overshadowed the tiny seedlings and cuttings (Fig. 4). Since that time, the plants have grown beyond our expectations and we have thankfully suffered very few losses (Fig. 5). This is in no small part due to the situation of the garden, which is in a protected valley around 20 metres above sea level with two semi-permanent creeks flowing through it. The soil here is comprised of alluvial topsoil overlaying weathered dolerite-derived clayey soil with an average annual rainfall of around 763 millimetres per year. Although we are situated at a latitude of around 43°S, our maritime island climate protects us from the most severe weather, but we do experience a few frosts each winter. Frosts have become less of a problem as plants develop and canopies thicken, although in the first few years we put ‘blankets’ made of shade cloth and bracken fern fronds over the tender young plants when we anticipated a frosty morning. Thick cypress and Acacia melanoxylon windbreaks have also strategically been planted to reduce potentially damaging northerly and southerly winds.

Figure 4. Picture of the Inala Jurassic garden when it first opened in 2014. Photo: T. Cochran. Figure 5. Picture of the same area of the garden as in Figure 4 taken in 2020. Photo: B. Moriarty.

Figure 5. Picture of the same area of the garden as in Figure 4 taken in 2020. Photo: B. Moriarty.

Over 50 plant families and around 700 species are now represented in the garden and include the conifer families Araucariaceae, Podocarpaceae and the subfamily Cupressaceae: Callitroideae (the southern cypresses), all of which are estimated to have originated in the Jurassic period around 200 million years ago. The ancient angiosperm families represented in the garden include the Winteraceae, Atherospermataceae, Proteaceae, Nothofagaceae and Myrtaceae which are believed to have originated in Gondwana 80−94 million years ago. Monocot representatives of Gondwanan flora such as the family Restionaceae (dating back to the Cretaceous period around 65 million years ago) are also featured as are taxa of probably more recent lineage such as the genus Libertia (family Iridaceae) of which we grow species from South America, New Zealand and Australia.

Strategic plantings have enabled us to create microhabitats where species from much warmer climes are growing, such as the Firewheel Tree Stenocarpus sinuatus, Macadamia Macadamia tetraphylla and several New Caledonian species. We are also having good success with high altitude species at lower latitudes such as Wilkie’s Leatherwood Eucryphia wilkiei (Fig. 6). This is a relatively newly discovered species restricted to the cloud forest on top of Mt Bartle Frere in the wet tropics region of north-eastern Queensland. Our specimens are already producing flowers and viable seed from which we are growing new seedlings. We have also managed to convince species such as Blue Mountains Pine Phaerosphera fitzgeraldii Figure 6. Eucryphia wilkiei, a to grow here despite the absence of spray zones of waterfalls member of the family Cunoneaceae on the sandstone escarpments of its natural habitat. Another found in the cloud forests in north Queensland which is growing species with which we are having great success is the Wollemi and flowering in the Inala Jurassic Pine Wollemia nobilis. In addition to the two original plants Garden. Photo: T. Cochran. that I purchased around 10 years ago, over the past few years we have ‘adopted’ several additional large potted specimens from members of the general public who can no longer look after them. We are thrilled to watch these rather bedraggled, nutrition-deficient, pot-bound plants thrive after being planted in the garden (after a couple of months of quarantine). They are now rewarding us with luxuriant growth and masses of both male and female strobili from which we are now harvesting and germinating viable seed and successfully striking cuttings for mass plantings.

Figure 6. Eucryphia wilkiei, a member of the family Cunoneaceae found in the cloud forests in north Queensland which is growing and flowering in the Inala Jurassic Garden. Photo: T. Cochran.

We also grow most of the Tasmanian endemic plants with Gondwanan connections including many alpine species such as the monotypic Mountain Rocket Bellendena montana (Fig. 7). Native Plum Cenarrhenes nitida and Creeping Strawberry Pine Microcachrys tetragona. We have found King Billy Pine Athrotaxis selaginoides difficult to grow and have learned that it prefers a more shaded position, at least when it is small, than the Pencil Pine Athrotaxis cupressoides and Summit Cedar A. laxifolia which are growing at a much faster than expected rate, even though the latter species is believed to be a natural cross between Pencil and King Billy Pine.

Figure 7. Mountain Rocket Bellendena montana, a monotypic Tasmanian endemic basal member of the family Proteaceae in the Inala Jurassic Garden. Photo: B. Moriarty.

In addition to labelling every species, interpretive signs for each family have been installed throughout the garden and the entrance sign includes an introductory explanation on Gondwana and the theory of plate tectonics to give context. The Inala property manager Steven ‘Bori’ Morris and I also run guided tours of the garden for those people who request additional interpretation. The content of the tour varies according to whether the visitors are school and community groups, garden societies, private individuals or those with a more academic interest. In all cases, we aim to provide education, increase awareness and contribute to conservation. The latter is undertaken by growing as many species as possible that are threatened in their natural environment with the aim of providing insurance specimens and perpetuating the species through provision of stock plants to other botanic gardens throughout Australia. These two philosophies underpin our business ethos at Inala, from covenanting the natural forest on the property, to the aims of our ecotourism company. The garden is open to the public and entry fees and sales from the adjoining gift shop which sells local crafts and books contribute to the Inala Foundation for the conservation of natural habitat and threatened flora and fauna. The garden is also complemented by the adjacent Inala Nature Museum, which contains fossilised representatives of some of the extant taxa growing in the garden. The garden logo was created from merging an image of the foliage of a living Wollemi Pine Wollemia nobilis which is growing in the garden and a 175-million-year-old Jurassic fossil of the extinct species Agathis jurassica which shows the morphological similarity between the foliage of these two members of the Araucariaceae (Fig. 8).

The garden joined BGANZ in 2019 and I attended the 9th BGANZ Congress in Wellington, New Zealand in October 2019 with the generous assistance of a BGANZ travel grant, as the small entry fee that we charge for the garden contributes to a small percentage of the cost of running the garden, which is predominantly self-funded. I was truly inspired by the breadth of topics covered, the depth of combined knowledge and commitment of attendees at the congress. The conservation theme of the congress fitted well with the ethos of my other enterprises and reinforced my ambition for the garden to contribute in some way to conservation.

Figure 8. The Inala Jurassic Garden logo was created by merging a terminal branch and developing male strobilus of Wollemia nobilis and a 175-million-year-old fossilised specimen of Agathis jurassica to demonstrate the connection between living and extinct Gondwanan species.

As we all know, Covid struck in force here in Australasia in March 2020 and my ecotourism business was forced to a grinding halt. International clients form 80% of our business, so it was time to become more inventive. The unexpected downtime from my usual tourism focus provided the opportunity for me to turn my full attention to the garden and make some further decisions regarding the best way to prioritise our conservation focus. During this period, the garden joined Botanic Gardens Conservation International (BGCI), the Climate Change Alliance of Botanic Gardens and the International Association of Botanic Gardens (IABG). I was also inspired by the Tropical Mountain Plant Science (TroMPS) and ex situ Conservation Project, a collaboration between the Australian Tropical Herbarium (ATH), the Australian National Botanic Garden Canberra, Australian Rhododendron Society (Victoria), Brisbane Botanic Gardens, Cairns Botanic Garden, Earthwatch, Royal Botanic Gardens Victoria, Royal Botanic Garden and Domain Trust (Sydney), Western Yalanji (and other indigenous groups) and the Wet Tropics Management Authority. This project focusses on establishing ex situ collections of Far North Queensland cloud forest plants, encompassing a broad range of endemic flora, including relicts of Gondwanan species of flowering plants, conifers, ferns, mosses and other non-flowering taxa. Climate modelling predicts these peaks will become hotter with far less reliable precipitation. Given that these target species occur nowhere else on earth, establishing secure, genetically diverse populations in botanic gardens in ex situ holdings is crucial. Such exciting and valuable plant conservation initiatives are a perfect fit for the conservation focus of the garden and we are proud to be involved in the project.

In November 2020 I applied for a grant offered by the Global Genome Initiative for Gardens (GGI-Gardens) and the United States Botanic Garden (USBG) which was administered through BGCI. The grant’s aim was to support activities to preserve Earth’s genomic biodiversity of plants through sampling of living collections maintained at botanic gardens around the world. As I researched the criteria for the grant, I realized that we had over 100 species of paleoendemic Tasmanian and other under-represented taxa in the garden’s living collection that are currently missing from the Global Genome Biodiversity and Genetic Sequences databases. This enabled the garden to be selected as one of the 14 successful botanic gardens and arboreta from nine countries around the world. Inala team member Dr Catherine Young is assisting me in collecting genetic samples and preparing voucher herbarium specimens which will be lodged and stored in perpetuity in the Tasmanian Herbarium near Hobart for use by researchers from around the globe (Fig. 9). We are excited and proud to help build capacity and provide resources for global plant biodiversity genomics research and to support conservation and preservation programs through our small garden. This project aligns well with our other conservation-based work through our not-for-profit organisation the Inala Foundation and our ecotourism enterprise.

Figure 9. Catherine Young and Tonia Cochran preparing voucher specimens for the GGI-Gardens and USBG-funded award administered through BGCI.

Throughout the process I have been lucky to have the help of a good team, including the Inala property manager ‘Bori’, who spends much of his time in the garden planting and mulching, Brad who mows and takes photographic records of the plants and Jude, a retired arborist who kindly donates her time and considerable pruning skills. I am also grateful for the help of our volunteer weeders who have been of invaluable assistance in keeping the garden looking great, which is so important for a garden that is open to the public and especially important now that the main source of funding from the garden − my ecotourism business − is facing Covid-related challenges.

Besides its aesthetic appeal and educational value, the garden is hopefully also of use as a repository for seedstock and threatened species with the aim of holding insurance specimens and sharing material with researchers and other botanic gardens around Australasia. I would welcome collaboration with interested BGANZ members so please don’t hesitate to contact me at inalajurassicgarden@gmail.com.

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