Tasmanian Plants

Since time immemorial, mountains have held special meaning to humans, and coming from a place where the tallest point in the landscape was a measly 169m high, I took the first available opportunity to visit the most accessible mountain when I arrived in Hobart. Thus began my love affair with Mt Wellington. Mt Wellington became my outdoor classroom. I frequented the walking tracks on mountain but I never walked far due to my photographic compulsions. Whatever little distance I managed to cover on foot was sufficient to convince me of the diversity of botanical life on the mountain. Browsing through the scientific literature, I was amazed to discover that the Mt Wellington Range was a stronghold for about a third of Tasmania’s higher plants and up to 60% of Tasmania’s bryophyte flora. I was duly impressed. Appreciation grew.

Those years back when I was doing my undergraduate course, Dr Rob Wiltshire conducted an excursion up the mountain as part of an ecology course to show sophomores the adaptations of eucalypt species to altitude. The class was brought up to the subalpine woodland to look at how eucalypt seedlings cope with frost and excess light. The exercise involved some walking and I took the opportunity to look around for anything flowering. By that stage of my academic life, I must have, I believe, unwittingly gained a reputation for being an incessant questioner, particularly when it came to the identity of plants. Perhaps Rob wanted to silence me before I could ask anything and he pointed to a dark handsome silhouette of a shrub on the rock boulders by the roadside and exclaimed, “Ahhh, do you know what that is?” Of course I did not but I took a stab at it anyway and I was That was when Rob sagaciously replied, with an inflection I can only imagine was meant for dramatic effect, “That’ll be the rare endemic tree daisy, Brachyglottis brunonis.”

I was duly impressed and intrigued. Members of the sunflower family (Asteraceae) such as daisies and groundsels are usually thought of as herbs, particularly in European countries, but then in temperate Australia, tree daisies appear to be a common theme. I learnt later that the tree was named after famed Scottish botanist Robert Brown, hence the specific epithet ‘brunonis‘. Vernacularly, the tree was known variously as the Tree Groundsel, Tasmanian Daisytree or Brown’s Tree Daisy. Interestingly, the only other species of Brachyglottis occur in New Zealand.

My reveries on daisytrees were short-lived in the face of academic pressures. Visits to the mountain trickled.

The final year of my undergraduate studies arrived and one academic unit which piqued my interest was Plant Science Research, in which I would get a chance to try out a mini-project of my own. I toyed with the notion of studying a rare or endemic plants and I felt again the call of the mountain, and remembered the Tasmanian Daisytree, which was both rare and endemic. I sought Rob out and he graciously agreed supervise me on the academic endeavour. We fine-tuned the objectives of the study, which would be to furnish an explanation on why the Tasmanian Daisytree is rare within it’s habitat range. The Tasmanian Daisytree is limited to Mt Wellington and a few other nearby locations. It’s distribution does not exceed 50 square kilometers and it is further restricted only to subalpine woodlands. In it’s habitat, it is also found scattered in a very disjointed manner and there was no obvious reason why this should be so since the subalpine habitat was apparently rather uniform. When we eventually analysed the data we collected and compared the vegetation and environmental factors of areas with and without the Tasmanian Daisytree, little useful information emerged. Areas with and without the Tasmanian Daisytree were not extremely different in terms of their vegetation or environment. Other forces must be responsible for preventing the Tasmanian Daisytree from attaining ubiquity! As far as speculations go, the Tasmanian Daisytree is probably stopped cold in it’s tracks at the seed or seedling stage. We did notice in our preliminary surveys that seedlings of the tree daisy were exceedingly rare.

Limited as the study was, more questions were raised than answered, which is, as I have come to believe, a trend that drives the heartbeat of scientific inquiry. Why the Tasmanian Daisytree chooses to be where it is may remain a mystery for some time and I hope to see one day when I sleuth through the scientific literature, a paper on the lines of: Towards an explanation of the rarity of Brachyglottis brunonis.

In all likelihood, the Tasmanian Daisytree originated on the mountain, and has never managed to move far. It’s rarity only serves to endear one to it’s presence, and presents the all so pleasurable challenge of spotting it among the ocean of other common plants. I can see the Tasmanian Daisytree as no less than the mascot tree of Mt Wellington, the prime botanical feature of Hobart’s Table Mountain. I imagine that the great nature photographer Peter Dombrovskis might thought similarly of the iconic status of the Tasmanian Daisytree when he immortalized in one of his great photographs, a scene of the tree against a backdrop of the weathered face of the Organ Pipes that so characterizes the mountain.

I envision that all genuine nature-loving Tasmanians should come to know the iconic tree of the Mountain that oversees Hobart. But the surest way to get acquainted with the tree daisy is still via a guide. You must be asked to look, and given ample opportunity to feel and smell, for it is likely that only then will you recognize. Then, even without it’s brilliant yellow blossoms you will see and recognize the distinctive dark shiny leaves, it’s charismatic branching and the sweet scent of it’s foliage. And forever will it be burned into your memory when your guide then utters in utmost authority: “That’ll be the rare endemic tree daisy, Brachyglottis brunonis.”

(Dedicated to Dr Rob Wiltshire)

It is most remiss of me, that I should write of one of Tasmania’s most iconic trees only now, after more than a year of blogging about Tasmania’s fantastic flora.

Introducing a tree that needs little introduction – Tasmania’s one and only deciduous native tree, the inimitable Nothofagus gunnii, the Deciduous beech, the Tanglefoot. There are those too, who simply call it the Fagus.

The Deciduous beech is a small tree from the beech family (Fagaceae). It reaches little more than 2 meters at the slightly lower altitudes but practically sprawls over boulders in the alpine zones. It is a mere dwarf compared to it’s much more widespread relative, the Myrtle beech (Nothofagus cunninghamii).

The legacy of the Deciduous beech however predates that of the Myrtle beech. As far as geological time is concerned, the latter is a much younger player in the biogeographical game.

Fossils very similar to that of the modern day Deciduous beech have been found in Antarctica, which leads one to conclude
very similar species were in Antarctica before Australia separated from that now snowed out landmass.

The deciduous nature of N. gunnii also leads one to think that deciduous-ness might have been a much more common feature of the Tasmanian tree flora in times past.

Alas, this is not really the easiest plant to visit. The Royal Tasmanian Botanic Gardens (RTBG) has at least one specimen, but it is a small one hardly more than 50cm tall, and it is largely obscured by other plants.

Obscured! That’s criminal, particularly given that an illustration of the deciduous beech graces the signboard at the entrance of the RTBG. Still, that is one of the closest places to civilization that one may visit this icon.

Most understandably, the Deciduous beech must be one of Tasmania’s most difficult-to-cultivate icon. It takes a long time to grow, if it even survives. Still, once it harmonizes with a sincere plants-person, a most exquisite bonsai plant the Deciduous beech will make.

But the connoisseur will seek the Deciduous beech in it’s highest abode. The true seeker must travel to the mountains to the west, during April of the Austral fall. They must drive west bound, up windy beaten roads, through the grand forest of the Mountain Ash. And where the road ends by the Dobson Lake, they must by foot alone traverse boulder and tarn, beyond where the highland gums surrenders to frost and exposure. Then, and only then, does the sincere seeker arrive at the Tarn shelf, a true mecca of nival endemicity, where the deciduous beech basks upon the alpine boulders in it’s most exposed, most brazen magnificence.

And then one may say that one has witnessed the leaf fall of the last of Tasmania’s deciduous, the yellow of the autumn Fagus.

Leaves of the Fragrant Candlebush become 'incontinent' with age

There are more similarities between plants and humans than we give credit for. Introducing the concept of incontinence in plants!

Leaves are the key parts of a plant which carry out the important act of water exchange with the environment. This being so, how effectively a plant can use water depends on how the easily water vapour gets from inside the leaf through the cuticle (the covering cell layer on the surface of a leaf) to the outside.

Greg Jordan and Tim Brodribb of the School of Plant Science, University of Tasmania have been studying the physiology of plant leaves for some time now and in 2007 published a paper in the scientific journal Functional Plant Biology on an interesting finding that the leaves of Agastachys odorata (Frangrant Candlebush or White Waratah) actually become incontinent with age.

Agastachys odorata is an endemic plant of the Protea family (Proteaceae) and occurs commonly in the high rainfall western Tasmania. The leaves of A. odorata exhibit distinctive annual growth increments, making different aged leaves easy to tell apart. The leaves are also very long-lived, with evidence of some leaves remaining on plants for up to 21 years. This makes A. odorata a fabulous choice for studying plant water relations with regards to leaf age.

Greg and Tim wanted to test the hypothesis that water vapour leaks across plant cuticles more readily as plant leaves age. In A. odorata they found that the older leaves were less effective in controlling water loss and hence used water less effectively than younger leaves. The increasing permeability of the leaf cuticle is implicated as the cause for this but it is also likely that the ability to control stomata opening also decreases with age, much akin to poor urinary sphincter muscle control in sufferers of incontinence. Greg and Tim concluded that the decreasing ability to use water efficiently could be due to natural leaf damage that occurs throughout the life of the leaf.

When the leaves of A. odorata becomes too old, it is simply shed. After all, the plant has no lack of leaves to serve it’s physiological functions. If only humans had the luxury of replaceable urinary sphincter muscles.

In Tasmania’s heaths, herbfields, cliffs, lake margins and among cushion plant communities of the Northwestern and Central highlands lurk one of Tasmania’s most elusive botanical secrets – a little lily that hails from a botanical lineage of great antiquity.

First though, we must clarify what exactly is a lily.

The natural history and taxonomic relationships within the large family of lilies (Liliaceae) often vexed botanists in the pre-molecular age. After botanists became well accustomed to assigning the appellation of ‘lily’ to a great many species of plants, the molecular blade swiftly and decisively ended the empire of the the lily family. Asparagus (Asparagus spp.), the onions (Allium spp.), the pineapple lilies (Astelia) etc.,  became allied to other plant Orders (as will be elaborated in another post!).

Some of the remaining members of what was once the Liliaceae still remain in what is considered an Order of Lilies, the Liliales. However, the members of this once colossal lily family grouped into smaller families of their own.

One family of lilies, the Campynemataceae, is of paramount interest. Molecular work based of the gene sequences of the RuBisCo enzyme (rbcL) that is present in the chloroplasts of all plants, tells us that the Campynemataceae lineage is the oldest among all that can still be considered a part of the great lily order. In 2004, researchers Thomas Janssen and Kårl Bremer compared the rbcL sequences of representatives of the families in the Lily Order and estimated the Campynemataceae lineage to have come into existence some 117 million years ago, as a sister group to all other families of the Lily Order.

The lily I have deemed to be one of Tasmania’s most elusive botanical secret is Campynema lineare (Green Mountainlily), a representative of the Campynemataceae.

C. lineare is endemic to Tasmania and is the only species in its genus, and Campynema is one of the two genera in the family. The only other members of this family is a genus of three species, the Campynemanthe, that hails from New Caledonia.

C. lineare is a slender herb up to almost half a meter in height, but usually much smaller in highland areas. The leaves are linear as the specific epithet ‘lineare‘ suggests’ but highly inconspicuous when the plant is not in flower. The blossoms are scarcely 2 cm across, with yellowish-greenish floral parts, borne on a brownish stem. This combination does not help in making it stand out well from the surround vegetation. Before releasing pollen however, the bright orange stamens do stand out quite clearly against the greenish floral parts, but in most other respects, C. lineare is a rather inconspicuous plant and not largely different from what anyone would call a ‘lily’.

A casual observer would not have guessed that it is a relict of ancient lilies. Probably not even Jacques Labillardière, the french botanist who described the genus in 1805, guessed that he was beholding a botanical gem.

But the time of awareness is nigh. In this digital and molecular age, inconspicuousness can no longer be an excuse for the lack of recognition suffered by this marvelous plant. It is time for the little Green Mountainlily to take it’s rightful place among the ranks of Tasmania’s iconic plants. Like the Delicate Laurel (Tetracarpaea tasmannica), we must sometimes know of the historical significance of such plants before we can truly appreciate their contribution to botanical heritage of this land we call Tasmania, a home to plant lineages of great antiquity.

A single field trip up toward the Central Highlands offers plenty for a plant lover to see and do. One thing that must be done however, is to pay homage to the cider gums (Eucalyptus gunnii) of the highland areas.

This cider gum is a tree of immense significance to Tasmania’s natural history. It is aptly named the cider gum for it’s sap, which has been reported to be used by the aborigines to make a much relished fermented drink (see article). I  was way too late to experience the spring sap that allegedly drips from the tree inviting all to partake of it’s sweetness. What would I give to try that out! It would be one of the most direct means of communion with the cider gum. On this occasion however, my objective was merely to make an acquaintance with the Cider Gum in it’s natural abode.

I drove along the Highland Lakes road north of Miena hoping to catch sight of some cider gums. There are two known subspecies, both of which are endemic to Tasmania. The more common one, E. gunnii subsp. gunnii (simply referred to as the cider gum) is well distributed throughout the highland regions of the southeast, central, and western Tasmania. The other subspecies, E. gunnii subsp. divaricata is known as the Miena Cider Gum, and has a much more restricted distribution to a small area around Miena around the Central Highland lakes. It’s status as a subspecies of the commoner cider gum was only recently elucidated in a publication by Prof. Brad Potts, Dr Wendy Potts and Dr Gintaras Kantvilas in 2001. Previously, the Miena Cider Gum was known as Eucalyptus divaricata.

I practically screeched to a halt when I sighted just by the side of the road, two large and stately trees which I suspected might be the Miena Cider Gum.

I got out and scanned the surrounds. There were quite a number of dead trees in the vicinity but these two trees were different. They exuded a vibe of vitality. I studied them intently, looking out for characters that might give me an opportunity for identification.

A low hanging branch gave me access to photograph a cluster of their leaves and their capsules. The adult leaves also had a slightly pale whitish (glaucous) appearance and there was the persistence of very glaucous, rounded and oppositely arranged juvenile leaves.

Prof Pott’s paper had mentioned that the capsules of the Miena Cider Gum also tend to be more glaucous. The capsules are supposedly a slightly more sub-urned shaped compared to the more consistently bell shaped capsules of the commoner subspecies.

The combination of characters of the Miena Cider Gum seemed to match the specimen I was looking and I am happy to conclude that that was what my specimen was.

More important than the dry an technical act of nailing an subspecific identity to the tree however, was the feeling of communion. Few experiences compare to an acquaintance with trees of such haunting magnificence and presence. There is no words for it, only feelings that linger. Silence would probably make the best conveyance of this.

When ardent students of mosses or bryologists traverse the globe to come to Tasmania, they will have, among the top candidates of their ‘to-see’ list, an `endemic Tasmanian moss. This is none other than Pleurophascum grandiglobum.

Rest assured that this moss lives up to it’s grandiose name. As this moss is so distinctive and significant, I’ll take the liberty to call it the Globe Moss, a name that I will use henceforth.

The moss was first described by Sextus Otto Lindberg in 1875, an early bryologist, in the Journal of Botany. He wrote (annotations in parentheses mine):

‘I Have to-day received from my friend Baron F. von Mueller, the renowned Director of the Botanic Gardens of Melbourne, a small tuft of a Moss, gathered this year by Mr. Robert Johnston on turfy soil near Picton River, in Tasmania. This Moss is of the highest importance, indeed of no less interest to the Muscologist (moss specialist) than is Rafflesia or Welwitschia to the Phanerogamist (higher plant specialist). It is, in fact, a very robust Phascaceous (bud-like) plant with the fruit perfectly lateral on the stem! I dare not as yet call it truly pleurocarpous (fruiting from specialized side branches), as its affinity is most obscure; but as it has, as far as I know, not been described, it ought to be called Pleurophascum grandiglobum…’

The Globe moss appears to be largely restricted to Buttongrass sedgeland habitats in the western part of the state. In a sterile state, the leaves are beautifully and symmetrically arranged around the stem and from the top look like the way lotus petals are arranged around their flower axis. The leaves are almost cup-like, lack nerves, but usually, although not always, have a single hairpoint at the apex. These characters, with the additional habitatual context, renders the Globe moss difficult to mistake for anything else.

When this moss is in fruit however, it is most unmistakable! The green spherical capsules, which ripen a dull yellow-brown, are 3-6mm in diameter, and are possibly among the largest, if not definitely the grandest, of all mosses in Tasmania. These grand structures that gives the moss it’s specific epithet ‘grandiglobum‘ are borne proudly on long setas (or stalks).

The capsules are cleistocarpous, a sophisticated way of saying that it does not open regularly through a well defined mouth, but rather, splits open irregularly at maturity. Precious little is known about the dispersal mechanism of the spores, much less on why the moss appears to be restricted to Buttongrass sedgeland habitats.

There are other reasons as to why the Globe moss is of such botanical interest. The distribution of the members of Pleurophascum are highly disjunct. One species P. ocidentale occurs in Western Australia. Another species, P. ovalifolium, occurs in New Zealand and was only recently determined by Australasian bryologists Alan Fife and Paddy Dalton in 2005 to be a different species from P. grandiglobum.

The affinities of Pleurophascum to other mosses are unclear. Bryologists have variously proposed that it is related to the Bryum (the Bryaceae) or Pottia (the Pottiaceae) mosses, but until more convincing evidence surfaces, it is best that the Globe moss remain in a family of it’s own, the Pleurophascaceae.

If there should one day be an international exhibition of mosses, where every country were to submit a portraiture of a unique indigenous moss for exhibition, there can be little doubt that the Globe moss will be the prime candidate to represent Tasmania’s bryological heritage. As far as mosses go, the Globe moss puts Tasmania on the world map.

Hybridization as a means of making new species is not an uncommon concept and hence it must be applicable to other species. I present a case using a Tasmanian example – the Olearia daisybushes.

Olearia is a large and conspicuous genus of shrubs in the sunflower or daisy family (Asteraceae) with some 23 species in Tasmania of which 8 are endemic to Tasmania (not counting subspecies).

Left: Geebung Daisybush (Olearia persoonioides); Right: Prickly Daisybush (Olearia pinifolia); Centre: Possible hybrid

Two of the endemic species are of interest in this post: Olearia persoonioides (Geebung Daisybush) and Olearia pinifolia (Prickly Daisybush). Both are common and largish daisybushes that grow in subalpine woodlands.

Whilst botanizing at various spots around the Central Highlands I stumbled upon the two species of daisybushes growing in close proximity in the understorey of a eucalypt woodland. They were both in full flower. At the same time I also noticed numerous specimens that looked like intermediates between the two.

While this intermediate specimen deserves much more detailed study, I have prepared a set of photographs and made a table of the characters comparing the two daisybush species with the intermediate specimen.

Many additional aspects of the morphology of the intermediate specimen deserves study. For example, the morphology of the flowers and fruits (achenes) needs to be examined in greater detail. Other studies like chromosome counts might also be helpful in determining the hybrid status of the intermediate specimen.

A trip to the herbarium is in the works!

The Blue Gum (Eucalyptus globulus), Tasmanian Waratah (Telopea truncata), Deciduous Beech (Nothofagus gunnii), Myrtle Beech (Nothofagus cunninghamii) and Pandani (Richea pandanifolia) are names that are often cited by plant enthusiasts and bushwalkers guidebooks as ‘must-sees’ of Tasmania.

But these five iconic plants, showy and famous as they are, must defer to THE ONE TRUE ICON plant that represents Tasmania — the Delicate Laurel (Tetracarpaea tasmannica). The popular portraiture of Tasmania’s botanical gems must be expanded to exalt the Delicate Laurel and to remedy it’s unfortunate oversight.

(Yes I am being evangelical).

The Delicate Laurel is by no means an uncommon plant. It occurs in wet forest or more often, subalpine shrubberies in the western mountains. The plant blends quite immaculately into the surrounding scrub and is not extremely prominent unless in flower, the erect flower stalks bearing small odd-looking white flowers with 4-5 oversized carpels (female parts). Without consciously looking for it however, Tetracarpaea would be quite easy to overlook whilst hiking pass the lush shrubbery vegetation. Once known however, the plant is easily recognizable by it’s thick leathery serrated leaves. The brown dry fruits (folicles) are also quite distinctive.

Distinctive as it is, the history of how the plant was named and classified has been fraught with difficulty and confusion (See Tasmanian Flora online profile).

The eminent botanist Joseph Dalton Hooker is often attributed with having named and described the plant in but it has only recently been clarified that it was his father, Sir William Jackson Hooker that had found and described the plant (The original illustration of the plant in Sir William Hooker’s Icones Platarum may be found here). It was also only recently that the correct species epithet ‘tasmannica‘ was reinstated, as opposed to the commonly but mistakenly used ‘tasmanica‘.

Botanists also have had difficulty determining the affinities of this enigmatic little shrub. They variously thought it to be related to the Horizontal bush (Anodopetalum biglandulosum), the Native Laurel (Anopterus glandulosus), and even Saxifrages. Only recently have molecular methods demonstrated that the closest relatives of Tetracarpaea are actually raspworts (Gonocarpus spp. and Haloragis spp.) and watermilfoils (Myriophyllum spp.). Still, the unique traits of the Delicate Laurel dictate that it is best placed in a family of it’s own, the Tetracarpaeaceae.

So there we have it. A true botanical orphan found ONLY in Tasmania.

The ONLY species in the genus.

The ONLY genus in the plant family Tetracarpaeaceae.

A prime example of Tasmania’s botanical heritage.

Forget about beeches, waratahs, pandanis and blue gums for a moment. These long revered icons have been discussed, photographed, drawn and stylized in Australian art ad nauseum. A true connoisseur of plants visiting Tasmania for the first time must embark on a montane pilgrimage and pursue first and foremost the one and only Tetracarpaea.

Pimelea sp. nova Schouten Island. Photo on right shows the raised leaf scars.

The Royal Tasmanian Botanical Gardens is a constant source of botanical discovery for me. Every time I visit I discover something that I’ve never seen before. In my most recent visit I wandered over to the East Coast collection where I spotted a large robust shrub about 1.5m or so tall. To my surprise it was a species of Riceflower (Pimelea).

Pimelea nivea (Bushmans Bootlace)

Riceflowers belong to the Daphne family (Thymelaeaceae) from which we get our ornamental European Daphnes.

In Tasmania, Pimelea is represented by some 17 different species of shrubs that occur in habitats as diverse as coastal heath to alpine shrubbery.

The larger species of Pimelea in Tasmania are often called Bushman’s bootlace because of the tough bark that peels in stringy ribbons.

The riceflower that was growing at the East Coast collection was probably planted there a year ago. It is an as yet undescribed species that was collected from Schouten Island, an small island just off the tip of the Freycinet Peninsula on the East Coast of Tasmania. Given the locality of it’s discovery, I assume it must be a lowland shrub. It was labeled as “Pimelea sp. nova Schouten Island”, ‘nova’ alluding to it’s newly discovered status.

Pimelea sericea (Mountain Riceflower)

As first impressions go, the Pimelea sp. nova has the stature of the Bushmans Bootlace (Pimelea nivea). However, the leaves are have silky hairs on both the upper and lower sides unlike the Bushman’s Bootlace which is clearly hairless on the upperside and densely white hairy on the underside.

As far as leaf details go then, Pimelea sp. nova looks more like the Mountain Riceflower (Pimelea sericea).

However, the Mountain Riceflower is smaller in stature, has pinkish flowers, and as it’s name suggests, is a high altitude denizen.

Another rather distinctive feature of the Pimelea sp. nova are the raised leaf scars. From written descriptions, the Silver Riceflower (Pimelea milliganii) also has such raised scars. Other leaf attributes also match Pimelea sp. nova quite closely. However, the Silver Riceflower is also a high altitude species and only known from the western mountains of Tasmania.

The key characters then that distinguishes the Schouten island riceflower must be its robustness and its habitat. Still, I look forward to reading the formal description of this new and interesting species in the very near future.

As a little experiment, I made a short first time video on the Pineapple Candleheath (Richea dracophylla) last month. Note that I got the specific epithet wrong (I said Richea ‘dracophyllum‘) in the video.

It’s endemic, it’s delicious. What more can I say.