On today’s show we learn about the Nightcap Oak, a critically endangered flowering tree native to eastern Australia, in the northeast corner of the state of New South Wales.
Rough Transcript
Intro 00:05
Welcome to Bad at Goodbyes.
On today’s show we consider the Nightcap Oak.
Species Information 02:05
The Nightcap Oak is a critically endangered flowering tree native to eastern Australia, in the northeast corner of the state of New South Wales.
The Nightcap Oak’s scientific name is Eidothea hardeniana. And it is an ancient species. DNA studies suggest the genetic lineage of the Nightcap Oak is over 90 million years old, dating to the supercontinent Gondwana which split apart into South America, Africa, Antarctica, India and Australia.
The Nightcap Oak is a recently described species. Meaning that it was only confirmed and accepted as a unique distinct species in 2002. Botanists in the mid 20th c, having collected immature specimens, inaccurately categorized the species and it wasn’t until the early 2000s that new sample collection and gene studies by Peter Weston and Robert Kooyman confirmed its distinct lineage.
Weston and Kooyman write about their work in a way that captures some of the awe we reach for on this show. They write (quote):
“It is a large rainforest tree… It grows in a relatively accessible place - you can drive a family sedan to within 100 metres of a couple of the trees. It is a highly significant evolutionary relict. Isn’t it amazing that such a plant could evade detection until now? If the Nightcap Oak could hide so effectively, how many smaller, or less distinctive, but nonetheless important plant species are still lurking in our wild places, awaiting discovery?” (endquote)
The Nightcap Oak is a medium-tall tree, growing up to 130 feet tall. It usually develops a single main trunk, with a diameter of up to 2.25 feet though it is not uncommon for the tree to produce numerous subsidiary shoots, branching directly from its base. Its bark is a greyish-brown hue with a flaky texture.
As a sapling, when the tree is roughly less than 5ft in height, its leaves are orange to red in color and are toothed, each leaf bearing 10-20 sharp spines. As an adult though the leaves become dark green, with entire margins, so that means their edges are smooth, no spikes.
This is such a cool evolutionary strategy. While the young tree is short enough to be reached by local herbivores, ground level-browsers, it produces these spiky defenses and then as the tree matures and its canopy grows to heights above the reach of most herbivores, the tree adapts its leaf form prioritizing photosynthesis rather than defense.
The flowers of the Nightcap Oak are beautiful, and strange, and perhaps a little silly looking. I struggle to describe them, the buds look like a starfish made of marshmallow, an old-timey broach, a spilled bottle of aspirin. The flowers are white and grow in clusters, inflorescences of 7-11 individuals with tubular buds that open to thread-like stamen.
The Nightcap Oak is andromonoecious, meaning a single individual grows both male flowers (with pollen-producing stamen) and bisexual flowers (with both stamens and seed-producing ovaries). Flowering typically occurs in October and November (of course that is spring in the southern hemisphere). The flowers are pollinated by small nocturnal beetles, and once fertilized, fruit development takes over a year. The green-sih fruits grow to roughly full size in the following December. And then over the next few months their color shifts to a dull golden yellow, and the fruit falls from the tree in February or March.
These fruits are drupaceous, think stone fruit, like a plum. They have an exocarp (that’s the outer skin), a mesocarp (that’s the fleshy fruit middle layer), with a hard woody stone in the center (the endocarp) and inside the endocarp is the seed.
Researchers believe that the Nightcap Oak’s seed were historically distributed by larger mammals and birds that no longer exist in its range and so today, primary seed dispersal relies on native bush rats. Once the fruit falls to the ground, these rats chew through the fruit and stone to access and feed on the seeds themselves. Um, chewed up seeds obviously do not germinate, and so successful seed dispersal for the Nightcap Oak is dependent upon the “forgetfulness” of the bush rats. Fruits are collected and stored by the rats but some of these caches are misplaced, forgotten, allowing those seeds to potentially germinate.
The Nightcap Oak is also capable of vegetative reproduction, re-sprouting. The plant regenerates new shoots and stems from existing plant tissues after above-ground parts have been damaged or destroyed. So, for example, if the branches and main trunk are lost to fire, the plant can produce new growth at the top of the roots, the base of the stem, at or just below the soil surface. So individual trees can regrow rather than like dying entirely, and persist and propagate in this alternative asexual way.
Though I could not find conclusive documentation of its lifespan; multiple sources suggest that the Nightcap Oak could live to hundreds, perhaps even thousands of years.
————
In the dream
Beneath a near-unbroken canopy of green.
Moonlight whispers through the foliage.
And the night beetle takes her midnight wander
In the safer quieter before the rowdy chorus at dawn
And her short journey is one waymarker in incomprehensible time
she brushes against oak pollen, she brushes against oak pistil
And it begins
The oak makes sugar to offer the future,
In a slow fruit with an eager seed inside.
From green to yellow to plummet to the forest floor
To be gathered and forgotten and then to grow and grow
I too take a short walk in the moonlight, in these woods,
And I inhale and exhale one of the half a billion breathes of my short life,
(which is) Another offering from this ancient grove,
And I ache and marvel at the accident of being.
In the dream
————
The Nightcap Oak is native to eastern Australia, to the Nightcap Ranges, a mountain system located in the Northern Rivers region of the state of New South Wales. This region is part of the Gondwana Rainforests of Australia World Heritage Area, a unique bioregion home to many rare and ancient species.
The Nightcap Oak is found only along a single creek, on the southern side of the Nightcap Mountains, roughly 1000 ft above sea-level, and in a less than five square mile area.
This landscape is dramatic, both lush and rocky, with severe terrain, some valleys and gorges just 250ft above sea level and peaks, like Mount Burrell, over half a mile up. The Nightcap Range is at the southeastern edge of the Tweed Volcano, a massive long dormant shield volcano that erupted over 20 million years ago, shaping this habitat. And so soils here are acidic, derived from that volcanic rock.
This is a warm temperate rainforest. Warm temperate rainforests have cooler average temperatures and greater seasonality than tropical rainforests, though with similar high humidity and rainfall. This region sees summer highs in the upper 80s°F and winter lows dipping into the upper 50s°F. Annual rainfall can exceed 100 inches.
The Nightcap Oak shares it’s rainforest habitat with:
Green Catbird, Mountain Water Gum, Brush Box, Parma Wallaby, Pink Cherry, Strangler fig, Olivers Sassafras, Koala, Long-nosed Potoroo, Dorrigo Plum, Peach Myrtle, Rufous Bettong, Minyon Quandong, Albert’s Lyrebird, Crabapple, Pale-yellow Robin, Australian Logrunner, Blueberry Ash, Regent Bowerbird, Paradise Riflebird, Yellow-bellied Glider, Giant Barred Frog, Bush Rat, Coachwood, Giant Stinging Tree, Stringybark Pine, and many many more.
The most pronounced current threat to the Nightcap Oak’s habitat is fire. Warm temperate rainforests are not fire-adapted, the thin barked trees and their seedlings and saplings are particularly vulnerable to fire damage.
After a particularly dry and hot season, in late 2019, early 2020 the Black Summer fires burned an estimated 70,000 square miles of this region, affecting roughly 30% of the Nightcap Oak’s known range. Fire, at this scale, in this habitat is rare; the Black Summer fires were the largest recorded burn in the Nightcap Range in over 1000 years. And so while fire risk, in general, is relatively low, fire impact is exceptionally high. These fires killed about a third of the mature Nightcap Oak population.
Habitat degradation and competition also threaten the species. Invasive species like the fast-growing camphor laurel, competes with the Nightcap Oak for light, space and resources.
The small range and small population size of the Nightcap Oak also makes it vulnerable, susceptible to stochastic events, so like random or unlikely occurrences, like massive fires, other extreme weather, or disease outbreaks. Given the small population size, the loss of even a single tree significantly affects the species’ genetic diversity.
And so relatedly, human-induced climate change is an increasing threat. Human-induced climate change has shown to result in more frequent stochastic events, like extreme heat, severe drought, and wildfire.
Fortunately, all of the Nightcap Oak population grows within a protected wilderness, the Nightcap Range National Park and the species has seen significant conservation attention.
It is legally protected by the Australian government, and National Recovery Plans and Conservation Action Plans have been developed.
Habitat defense and restoration work is ongoing, including management of invasive species, weed removal, controlled burns, and wildfire response planning. In fact, during the 2020 Black Summer Fires, National Parks and Wildlife Service firefighters were dispatched specifically to defend the Nightcap Oak. Physically extinguishing fires on the ground, and supported by helicopter water dump to douse flames as they approached plant populations. Sometimes humans are amazing.
Under the guidance of the New South Wales “Saving our Species” program, offsite conservation has been initiated at the Firewheel Rainforest Nursery and the Australian Botanic Garden Mount Annan. More than 500 seeds have been collected for propagation with 50 seedlings cultivated thus far. 20 of those seedlings have been successfully reintroduced to secret locations in protected wilderness in the Nightcap Ranges. These sites were selected with climate resiliency in mind. These are suitable habitats, a few hundred feet in elevation above the current Nightcap Oak range, where conservation scientists hope that the cooler air temperature, higher rainfall and more stable weather, might allow the Nightcap Oak to persist as our planet warms.
Nevertheless the Nightcap Oak has been considered critically endangered on the IUCN Red List since 2020 and their population is currently in decline.
Our most recent counts estimate less than 115 Nightcap Oak remain in the wild.
Citations 26:12
Information for today’s show on the Nightcap Oak was compiled from:
Australian Journal of Botany v.70, 189-203. Baker Andrew G., Catterall Claudia, Wiseman Matthew (2022) “Rainforest persistence and recruitment after Australia’s 2019–2020 fires in subtropical, temperate, dry and littoral rainforests.” – https://doi.org/10.1071/BT21091
Australian Plants v.21 no.172. Weston, Peter &; Kooyman, Robert. (2002). “Eidothea hardeniana: Botany and ecology of the Nightcap Oak” – https://anpsa.org.au/newsletter/australian-plants-journal-vol19-to-24/
Ecology and Evolution v.15: e71251. McMaster, E.S., Dimon, R.J., Baker, A.G., Harre, C., Mallee, J., Maric, A., Richards, P., Wiseman, M., Ho, S.Y.W. and Rossetto, M. (2025). “Combining Spatial, Genetic, and Environmental Risk Data to Define and Prioritize In Situ Conservation Units.” – https://doi.org/10.1002/ece3.71251
The Guardian. Sat 12 Oct 2024. Readfearn, Graham. “They are relics of the Gondwana age but five years after Australia’s black summer these trees are dying a ‘long, slow death’”. – https://www.theguardian.com/australia-news/2024/oct/13/nightcap-national-park-rainforest-trees-age-bushfires-impact
The IUCN Red List of Threatened Species 2020: e.T112631200A113309140. Forster, P., Ford, A., Griffith, S. &; Benwell, A. 2020. “Eidothea hardeniana.” – https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T112631200A113309140.en
Journal of Ecology, 93: 906-917. Rossetto, M. and Kooyman, R.M. (2005), “The tension between dispersal and persistence regulates the current distribution of rare palaeo-endemic rain forest flora: a case study.” – https://doi.org/10.1111/j.1365-2745.2005.01046.x
New South Wales National Parks and Wildlife Service – https://www.nationalparks.nsw.gov.au/conservation-programs/nightcap-oak-conservation-project
Nightcap oak (Eidothea hardeniana) Conservation Action Plan. New South Wales Environment and Heritage, Department of Planning and Environment, ISBN 978-1-922975-30-0; EHG 2023/0036; January 2023. – https://www.environment.nsw.gov.au/publications/nightcap-oak-eidothea-hardeniana
Telopea. v.9. Weston, Peter &; Kooyman, Robert. (2002). “Systematics of Eidothea (Proteaceae), with the description of a new species, E. hardeniana, from the Nightcap Range, north-eastern New South Wales.” –
http://dx.doi.org/10.7751/telopea20024022
Wikipedia – https://en.wikipedia.org/wiki/Eidothea_hardeniana
For more information about Nightcap Oak conservation and New South Wales rainforest conservation in general, please see the New South Wales National Parks and Wildlife Service at https://www.nationalparks.nsw.gov.au/ and the non-profit Rainforest Rescue https://www.rainforestrescue.org.au
Music 28:10
Pledge 35:24
I honor the lifeforce of the Nightcap Oak. I will commit its name to my record. I am grateful to have shared time on our planet with this being. I lament the ways in which I and my species have harmed and diminished this species. I grieve.
And so, in the name of the Nightcap Oak I pledge to reduce my consumption. And my carbon footprint. And curb my wastefulness. I pledge to acknowledge and attempt to address the costs of my actions and inactions. And I pledge to resist the harm of plant and animal kin and their habitat, by individuals, corporations, and governments.
I forever pledge my song to the witness and memory of all life, to a broad celebration of biodiversity, and to the total liberation of all beings.
