Tuesday, 21 November 2017

Cruel (but fair enough for the) Plant

A little like the Common Milkweed whose propensity to leg-pull I mentioned a few months ago, the Cruel Vine has love-hate relationship with it's pollinating butterflies, moths and bees. To get to the nectar at the base of the flower the pollinator has to extend its proboscis deep into a wedge-shaped groove so narrow that the insect, or part of its proboscis, can remain jammed into the flower.

This is clearly unfortunate for the insect but you'd think equally so for the plant that not only kills its method of pollination but has a decaying animal blocking up its reproductive system. Not so, as local orchid expert Edith Coleman explained to her Victorian Field Naturalist audience back in 1935 ('Pollination in Australia of Araujia sericifera Botero', Vic. Nat. 52: 3-7).

Like the milkweeds, Cruel Vine, or Araujia sericifera, is a member of the Apocynaceae, a family of often milky-sapped, poisonous plants such as Oleander. The Cruel Vine takes this a step further by trapping insects in its flowers then exposing them to a toxic secretion inside the flower.  

We also call Araujia sericifera the White Bladder-flower, on account of the slightly inflated flower shape as you can see in the unopened flower above (it's also a little inflated at the bottom, within those large green sepals).

As for the name False Choko, that arises from the choko-like fruit produced if the flowers don't kill their pollinators before they finish the job. (The true choko, or chayote, is produced by Sechium edule, a member of the melon family, Curcurbitaceae.)

Presumably insecticide is not the primary objective of the Cruel Vine flower. Like milkweeds and other plants closely related to Araujia, the flower structure is quite complicated, with a system of openings and grooves that work like a peg, clipping the pollen mass onto part of the visiting insect.

In Araujia, rigid wings around the anthers - where the pollen is attached - are responsible for trapping proboscises and also whole smaller insects that are incapable of removing the pollen mass anyway. The former may just be collateral to deter the latter (who are of no value to the plant in terms of its future success) or they may be part of a cunning plan....

Edith Coleman spent at least five years watching her Cruel Vine flowers, counting and observing their insect visitors. In her garden, thousands of insects visited the flowers with a total of 12 bees, five moths and two butterflies becoming trapped and dying. Her neighbour's plant (a bigger one, with more flowers) trapped 15 bees in a single year, but no moths or butterflies.

Edith Coleman observed a range of visitations which might be summarised as:
1. The insect proboscis reaches the nectar and is withdrawn without being trapped or getting a clip of pollen. No value to the plant here.
2. The insect pushes its proboscis a little further (to find more nectar), releasing in the process a pair of pollen masses which are clipped to the proboscis on the way out. And there is a way out: the insect isn't trapped when it picks up this load on exit. Half way there for the plant.
3. An insect with pollen attached to its proboscis visits another flower and manages to get in an out without releasing the pollen or becoming jammed. Again no value to the plant.
4. An insect with pollen attached to its proboscis pushes that little bit further (again, to find more nectar), such that the pollen jams the proboscis in the flower slit. The pollen can fall off, allowing the insect to withdraw fully from the plant or, it can be left behind if the proboscis breaks or the insect gets trapped and dies. Bingo, pollination!

Coleman also notes that only once did she see an insect trapped that didn't have pollen attached to its proboscis. So from these observations it seems that the process works fine for the plant, and only sometimes not so well for the insect visitors.

Given the success of Cruel Vine in so much of the world, and the demonstrated rarity of self-pollination, its seems the plant does get pollinated with great regularity. It can clearly 'adopt' various local insects of the right size and shape to do its pollination work. In South Africa, and presumably here in Australia, it's the native honey bee mostly, with only a few moths and butterflies.

Honey bees are not native to where it grows in Brazil, although bumble bees are. However the colour, large size, nocturnal perfume and low nectar offer of the flowers suggest they are more attractive to moths. In a more recent study Gareth Coombs and Craig Peter suggest the Cruel Vine may attract a range of insects in Brazil, including large moths which may be the primary pollinators even though some don't survive the attempt (as observed by Edith Coleman).

The Cruel Vine's ability to accommodate insects other than moths, however, has been a large part of its huge success as a weed around the world. From the plant's point of view, it doesn't seem to matter that a few proboscis-bearing species are killed along the way.

Note: Neville Walsh kindly suggested this charming topic to follow up my  recent story of butterflies leaving a leg or two when they pollinate one of the milkweeds. Because it flowers in summer in the Southern Hemisphere I've had to source my images from the Wikipedia, except for the final image, used with permission from Hernán Tolosa and from his delightful website Flora Bonaerense.

Tuesday, 14 November 2017

Daisy drama in the botanic garden

The native Silver Daisy-bush, Olearia pannosa, grows naturally in South Australia and in Victoria but the namesake variant - subspecies pannosa - is restricted to, and quite rare, in what is now mostly farmland in South Australia.

A second variant, subspecies cardiophylla, named after its (slightly more) heart-shaped leaves, is found in South Australia and Victoria, where it is also rather rare and scattered in distribution. In addition to leaf shape, the varieties differ in the colour and orientation of the hairs on the very hairy leaves. We call this subspecies the Velvet Daisy-bush.

Like last week's boronia, this species grows very nicely outside the National Herbarium of Victoria in Melbourne Gardens. It was in full flower, and early seed set, in early October.

It's a big proportioned plant, and dramatic when it flowers in its dry forest habitat. Bushes can be up to a metre high, with the velvety leaves to 12 centimetres long and flower heads three to eight centimetres across. While daisies are rather common and often overlooked in our garden this one definitely stands out in the Australian bush, or your local botanic garden.

Perhaps surprisingly, individual plants live for more than 38 years, supported by long fleshy roots. Although good seed set is reported from places such as Anglesea, dispersal by seed has been described as generally 'limited'.

When Ferdinand von Mueller described these two entities, in 1853, he considered them separate species in a genus called Eurybia. A decade or so later the genus was absorbed into Olearia in George Bentham's major work on the flora of Australia and the distinction between the two species abandoned for some time.

In 1986, South Australian botanist David Cooke resurrected 'cardiophylla' but only as a subspecies of Olearia pannosa. We like the genus placement but we are now thinking Mueller may have been correct about the taxonomic rank, so the (mostly) Victorian subspecies may end up becoming a distinct species of Olearia.

Embedded in the nomenclatural haze of the Velvet Daisy-bush is another genus and species name, Steetzia muelleri, published by Mueller's friend Otto Sonder in the same year and same journal (55 pages later...) as Mueller published Eurybia cardiophylla. Unfortunately that genus name had been used already for a liverwort, so the Steetzia name became what we call 'illegitimate'.

If 'cardiophylla' is indeed raised to species level at some stage we can't revert to the name 'muelleri' because that name has already been used in the genus Olearia. Olearia muelleri is, as Neville Walsh reminds me, a happy member of the Victorian, South Australian, Western Australian and New South Welsh floras (and less happily, the Northern Territory if we can rely on an old herbarium record).

Tuesday, 7 November 2017

Mueller's warty, smelly and very Victorian plant

The Forest Boronia grows mostly in forests, or woodlands, of eucalypts and banksias. It started flowering in the Melbourne Gardens in late September and will stay in bloom across its range right through to the end of summer and even sometimes into autumn and early winter. Next to the National Herbarium of Victoria building, where I took these photos, it is now finishing.

From Sydney (and once Melbourne) botanist, Marco Duretto's 116 pages of 'notes' on Boronia from eastern and northern Australia (that is, leaving out the Western Australian bounty), we learn a bit about this species.

As expected, Boronia muelleri was named after the first Director of Royal Botanic Gardens Victoria, Ferdinand von Mueller, who collected the 'type' specimen from the upper reaches of Bunyip River in western Victoria. It was at first, in 1863, considered a variety of Boronia pinnata but eventually granted species status in 1924.  

Boronia muelleri pops into New South Wales, as far north as Eden, but is primarily a Victorian species, extending east from Buchan but also found in the Otway Range and central Gippsland. A more recently discovered population of 20 or so plants between Bacchus Marsh and Woodend is doubtfully native. (Boronia pinnata is a pure New South Welsh, from north of Eden.)

Our boronia - Victorian by geography and era of scientific discovery - can be a small tree up to 7 metres high. Although in its incursion into New South Wales it reaches only 3 metres at most. 

Like many Boronia species it has fern-shaped leaves, which we call pinnate. Also like many Boronia species, the leaves smell. In this case not unpleasantly so.

I can detect notes of pine, cardamon and perhaps guava, although I haven't eaten a guava for a while. I asked my colleague Neville Walsh, who has a better botanical nose, and he thought 'a background of citrus (leaning toward grapefruit), maybe a bit of camphor, possibly turpentine, with a slight flush of honey'. Either that, he said, or that 'general Australian Rutaceae (Boronieae) kinda smell'.

You'll note the warty glands on the leaf surface above. I presume these contain volatile oils such as 'elemicin', which has been extracted from the species. And these oils are what presumably combine to create the difficult-to-describe odour. 

The Aniseed Boronia, Boronia galbraithiae, was chipped off our species in 1993 by Neville Walsh and his colleague David Albrecht. It's a true Victorian endemic, only growing on the slopes of mountains near Mount Difficulty, north of Sale in the mid-east of the State. Compared to Boronia muellerii it has smaller leaves (the 'leaflets' sticking out the side are shorter) with finely toothed or ragged margins. Oh and it smells different, like fennel rather than that rather eclectic perfume we might call Eau De Boronia.

Tuesday, 31 October 2017

They give a fig in Brisbane

Brisbane's City Botanic Gardens, at the opposite end of Albert Street to the swanky Roma Street Parkland, is the neglected sister (or brother if you like) of Mt Coot-tha Botanic Garden. When that slightly more elevated garden opened 40 years ago it quickly siphoned off what was left of the horticultural and botanical investment in town.

At first glance it reminds me of Sydney's Royal Botanic Gardens, with the high-rising backdrop and limited topography, although at 18 hectares is is half the size of Sydney's, and Melbourne's, city gardens. Like these two southern gardens, it has specimen trees dating back to the mid nineteenth century.

Director of both the City and Mt Cooth-tha Botanic Gardens, Dale Arvidsson, is apologetic about the standard of care (although on the mend), the scope of the plant collection (watch this space) and the state of the majestic old trees (first aid is being applied).

In the Master Plan published in 2015 the City Botanic Gardens will become a welcoming destination at the south-eastern end of a greener Albert Street. The riverside will be swished up, like other parts of the Brisbane River frontage - although perhaps a little softer. The bit that excites me, and I think Dale, is sprucing up the heritage plant collections (mostly trees) and showcasing edibles and medicinals.

One great example of a great story tree is the one behind this sign, a macadamia. It's the first grown in cultivation and the beginning of the macadamia nut industry (although that story has a little less to do with Queensland and more to do with Hawaii). The sign singles out the European settlers but it's unlikely the species was farmed by the first inhabitants of Australia.

Each of the trees is now being treated like an old friend or family member (which ever makes you think of caring), with its own regime of watering, mulching and pruning. Rather than an urban forest or tree collection, which can be appropriate and admirable, this is a botanic garden populated by elders who need some extra support.

While interpretation isn't strong - that is yet to come - I did like the sign on this Peepul or Bo Tree (Ficus religiosa), planted in the 1870s and having one of its limbs repaired. After the usual yarn about Buddha and his path to enlightenment being shaded at a critical point by this species, there is a lovely paragraph goes like this: The pious Peepul Tree is similar to the expansive Banyan Tree, which is also growing in these gardens. They are both Indian fig trees, and they are both considered sacred, though the Peepul Tree will never equal the Banyan's tremendous dimensions, and the Banyan Tree will never match the Peepul's mystical charm.

So mystical charm it is then, despite the intensive care on its lowermost limb.

Not far away is an avenue of Weeping Fig (Ficus benjamina), whose buttress roots had been cruelly severed to allow transit through their middle. Not only that, but their label says they hail from Malaysia when now it seems they are a dinky di Queensland native as well.

Then there is this fig, whose name escapes me but perhaps it is the one that will always exceed the dimensions of the Peepul Tree, the Banyan Tree (Ficus benghalensis). Here the tree supports its loping limbs with aerial roots that drop down to the ground then solidify like a new trunk. In a public park these dangling roots are tempting to swing on, and in case outside its native forest a dry atmosphere or a thousand other uncertainties can mean the roots never meet the ground.

Solution? Use plastic pipes provide a conduit to the Earth and wrap the tender roots in soil within hessian. In time any metal props and the aerial-root scaffolding will be removed. The fence too may go.

These are just three examples of the attention being applied to trees in the City Botanic Gardens. No matter what is added along the riverside or to the collections, I think it will be the heart-felt care of such leafy elders that will make this particular botanic garden a winner.

Oh, that and the grown-up Pereskia, usually grown in a pot and one of the few cacti with leaves...

Tuesday, 24 October 2017

Manga's red pine a treat for children

Having never been to Japan I was immune to the romance of the Japanese Red Pine, Pinus densiflora. Until, that is, I saw the recent Katsushika Hokusai exhibition at the National Gallery of Victoria.

Sure I saw The Great Wave off Kanagawa, 50 views of Mt Fuji (including one at the rear of 'The Wave', and in background of the one I've featured above), and even the Giant Butterbur (Petasites japonicus) in one of Hokusai's manga books. All very interesting but what grabbed my attention was red-barked tree, clearly a pine, and clearly something rivaling the Mediterranean Stone Pine (Pinus pinea) in its striking form.

So I thought I'd look for one in our own botanic garden. As luck and planning would have it, we do grow a cultivar called 'Pygmy', in our approximately appropriately called Ponderosa bed. (The garden bed includes an old Pinus ponderosa, another pine species (Pinus mugo), a couple of She-Oaks, and some mat-rushes and grasses.)

The Ponderosa bed is just inside The Ian Potter Foundation Children's Garden and, apart from the Ponderosa Pine, planted since 2004. This (dwarf) Japanese Red Pine is one of the original plantings (although a little stressed at the moment the new growth looks healthy enough).

The Japanese Red Pine also occurs naturally in North and South Korea, where it is, naturally, called the Korean Red Pine. Those growing in North Korea and nearby Russia are sometimes considered different enough to be given another botanical name, Pinus funebris.

In both Japan and Korea, Red Pines cover large areas in pure stands. As in Japan, the tree has strong cultural importance in Korea. Not only is it mentioned in South Korea's national anthem, it turns out to be the most frequently mentioned species mentioned in 'tree-related proverbs' and folk stories.

Where the species extends into China there have also been some taxonomic interventions (i.e. new names) but these are not generally accepted.

Japanese/Korean Red Pine is closely related to the also more commonly planted Scots Pine (Pinus sylvestris), a European-Asian tree planted in a couple of spots on the eastern side of the Melbourne Gardens. Scots Pine has shorter, broader and waxy blue needles.

Both are important timber trees, with the Red Pine used mostly for paper these days, although also for underground mining supports and railway sleepers.

It is the bark, though, that sets it apart from most other pines, although not so much Scots Pine. The flaky outer layer is red, or orange-red, particularly on the upper parts of the trunk. Hokusai seems to have exaggerated the colour a little in his woodcuts but in the right light I'm sure the bark is bolder in colour than what I've photographed here.

In Japan the species is very popular in horticulture, with up to 100 cultivars available. You'll find it (I'm told) around shrines and places, as well as in bonsai. Traditional medicines make use of the needles and pollen.

I see 'Pygmy' described (incidentally as a cultivar of a form of Pinus densiflora called umbraculifera) as upright, globose (rounded) and 'very dwarf'. I'm not sure any of this terminology is contemporary but clearly this is a small form of the tree. Indeed the tree is rarely grown in Australia except in bonsai.

The form umbraculifera is treated as a cultivar name, 'Umbraculifera', by Roger Spencer in his Horticultural Flora of South-eastern Australia. Its name refers the flattened, umbrella-like crown of this variant. I'll keep an eye out on our specimen to see if it matures into an umbrella or a sphere.

Or maybe something far more eccentric and artistic, like the specimen portrayed by Hokusai.  I wonder what the children would prefer?

Tuesday, 17 October 2017

Small compensation for unfulfilled Chinese ginkgo quest

Last year I had to cancel at the last minute a trip to Shanghai, where I was going to attend a meeting at the Chenshan Botanical Garden. As part of that trip I had hoped to visit one of the two possibly natural – that is, not cultivated by human – populations of Ginkgo biloba, the Maidenhair Tree, near Tianmu Mountain.

Ginkgo, as most people call it (with a soft first 'g' in China and a hard first 'g' in Australia), is a single species with a deep evolutionary history. It is the remaining member of a group of organisms sitting alongside conifers, cycads and flowering plants, but belonging to none of those groups. It looks like a flowering plant but has motile sperm rather than pollen (more like ferns, cycads and conifers), carried by the wind and needing to land of a drop of moisture to fertilise the female ovule. The ‘fruit’ contains a seed inside a hard outer coating, all within a yellow and stinky fleshy layer.

Reading further on the natural distribution of the ginkgo, including Peter Crane’s monograph on the species called Ginkgo: The Tree That Time Forgot, I discovered that the more likely purely natural population – and there is considerable debate – is to be found in the Jinfo Mountain area near Chongqing. These trees generate from seed and there is more genetic diversity here than anywhere else in China.

And so last week it was with great anticipation I joined the field trip associated with the Chinese Association of Botanic Gardens meeting in Chongqing to Jinfoshan, the Jinfo Mountain. I was in Chongqing as a guest of the Nanshan Botanical Garden, with whom I signed an MoU for cooperation with the Royal Botanic Gardens Victoria. Yet again I was fortuitously placed to visit this fascinating plant in its home territory.

Sadly the weather, and my ability to communicate in Chinese, let me down.

As you can see, the weather was what we describe in Australia as ‘foul’. The entire mountain was enveloped in mist and a gentle to steady rain persisted for the entire time we walked along the summit paths.

It seems I was probably nowhere near to where to the ginkgo grow anyway, so hail or shine I would have not have achieved my goal. The ginkgo grows in a band around the mountain at 470-1,500 metres above sea level. We were wandering around in the mist at 2,100 metres above sea level (about the same height as Australia’s tallest peak, Mount Kosciuszko).

Of course, this being China there are some planted trees here and there, including here, not far from the start of the cable car to the summit, near to the welcoming sign at the top of this post. This may be as close as I get to a ginkgo in its natural habitat...

There are, according to the abstract of a paper by Li Jianwn from Beijing and his colleagues from the Medicinal Botanical Institute of Chongqing City (which I think may be different to the Chongqing Institute of Medicinal Plant Cultivation which I visited on the way to the mountain), 300 or so very old ginkgo trees in the area, at least 10 thought to be over a thousand years old. The oldest - called Ginkgo Empress – is estimated at 2,500 years and has a girth of 35 metres.

So, no naturally growing ginkgo for me, yet. On the return trip we stopped for dinner at a reconstructed village of the local ‘ethnic minority’. There we saw planted ginkgo, and also many penjing (bonsai) specimens, including various leaf-shape cultivars.

I read on a tourist website that ‘when sunshine falls on [Jinfo Mountain], it looks like a giant Buddha shining with boundless golden radiance, hence the name, which literally means Golden Buddha Mountain’, and that ‘the Golden Turtle Facing Sun Platform in the north’, which we visited, ‘is a mountain edge looking like a golden turtle in the light of the sun’. On my visit there was, sadly, no sunshine and therefore no visage of Buddha or a turtle. We did see the large natural caves, and through the mist a few local plant species.

No trip is ever wasted and I’m sure there is aphorism around leaving some things in life not experienced. In fact I expect the Chinese have a way of saying it quite pithily. But still, I hope to one day try again.

Tuesday, 10 October 2017

Giant sea leaves near the lake

"With me tonight, to explain why this giant-leafed plant is almost incorruptible, is Green's spokesperson Ms Grandleaf Sea Grape...".

OK, not quite up the standard of our local television (ABC TV) darling Shaun Micallef, but the common name for Coccoloba pubescens - yes, Grandleaf Sea Grape - did set my mind wandering in this direction. Or was it to Middle Kingdom?

Back in Victoria, Australia, I doubt you will find this species in conversation or in reality. We don't grow this, or indeed any of its kind (Coccoloba) here in the Royal Botanic Gardens Victoria. We do grow other members of the buckwheat family, Polygonaceae, including a few I've blogged on here such as St Catherine's Lace and the Centipede Plant. We also employ one of the world's leading experts on the family, Dr Tanja Schuster.

Grandleaf Sea Grape, or Eve's Umbrella, though, is a plant I only recall seeing once, tucked inside the entrance of this glasshouse in Geneva's botanic garden, Conservatoire et Jardin Botaniques Genève. That's Geneva, Switzerland, is on the banks of Lac Léman but no where near the sea.

There are more than 150 species of Coccoloba, many of them producing clusters of grape-like fruits and quite a few growing by the coast. Hence Sea Grape, a common name applied to various species of Coccoloba. Other local names for this group of species stick with the marine viticulture theme: e.g. Little Beach Grape, Beach Grape Tree and Edge-of-sea Raisin Tree. Less obviously, some species are called Pigeon Wood, Big Potato and White Big Bed.

Nearly all Coccoloba species are from tropical America, with Coccoloba pubscens - our Grandleaf Sea Grape - native to Mexico, Guyana and the West Indies. Fittingly, it seems to have the biggest leaves in the genus, often half a metre wide and sometime bigger. The juvenile form of the plant, which is probably all we'll see in glasshouses, is larger leaved.

The eighteenth century Dutch botanist, Nikolaus von Jacquin, described the mature tree as inelegant but others focus on the beauty, or at least the function, within. The wood is said to be 'almost incorruptible' and when buried beneath the ground - as footing for fence posts for example - can become 'hard as stone'.

Like most of the buckwheat family, the Grandleaf Sea Grape has a distinctive sheath (an ocrea or ochrea) wrapped around the stem, extending upwards from where the leaf arises an. In the close-up below you can see blackish dry flaps which are part of this sheath.

While not in our glasshouses (yet), the Grandleaf Sea Grape has been grown in the conservatories of the UK since 1590, although not flowering until 1832. At that time, due to the 'bad condition of the hothouse' plants did not fruit or set seed.

Tuesday, 3 October 2017

Well hung orchids give Turkish ice-cream its stretch

They say you can tow a car with a rope of the elastic ice-cream made from orchid tubers. But then they say a lot of things.

This particular achievement was assigned to the 'legend' category by The Sunday Age restaurant critic Dani Valent in her recent review (20 August 2017) of a new Turkish ice-cream stop in Northcote called Cuppa Turca.

Turkey is the place for tough and stretchy ice-cream (dondurma), traditionally elasticised with an extract from the tubers of orchids called salep (or sometimes Sahlep or sahlab). As I mentioned in passing last year, the underground storage and over-wintering part of some Orchis species are ground into a flour which is included in drinks and sweet foods.

It seems a cup of salep was popular in the Ottoman Empire, making its way later to England in the 17th and 18th centuries, where it was called saloop. But, as you might have guessed, relying on the rather small tubers of a not particularly common plant has its consequences. In Turkey wild orchid populations have suffered through over harvesting and the product is now banned for export from that region.

In their mildly indulgent The Book of Orchids, Mark Chase, Maarten Christenhusz and Tom Mirenda state that all ground orchids in many parts of Turkey are becoming rare due to unsustainable harvesting for salep. To meet the demand within Turkey, collecting has extended into neighbouring countries with potentially similar results.

According to Wikipedia, the Romans also partook of saloop, preferring to call it satyrion and priapiscus, a reflection of its presumed aphrodisiacal properties. I'm guessing this has a bit to do with a pair of tubers sometimes looking like testicles, which the Greeks called orckhis (hence Orchis and orchids).

Today though, orchids and their testicles are in short supply. The new ice-creamery in Northcote uses a salep substitute, 'a secret recipe that replicates the original'. The product is 'stretchy and smooth and melts very slowly, just like the real thing'.

So what about the real thing, these orchid tubers. The Australasian Native Orchid Society packages up the excess tubers produced from cultivated plants, distributing them to members so they can grow their own.

Not all orchids have tubers, or tuberoids as they are sometimes called, but most Victorian species do. In fact of the nearly 400 species of orchid in Victoria, all but a handful produce tubers or at least fleshy underground roots of some kind. Those that don't are the larger rock and tree orchids.

Southern Australia is definitely the place to go for tuberous orchids. Not that I'm saying there is a potential salep market to be had. Far from it. Many of these species are rare and threatened, and all are protected against collecting on public land. But it makes you think, of ice-cream and other things.

Images: A couple of local tuberous orchids from Victoria (the Spotted Sun Orchid, Thelymitra ixioides at the top; a spider orchid, Caladenia valida, above; and protected by my son Jerome a few decades ago, the Wallflower or Donkey Orchid, Diuris orientalis) plus from the web an image of Orchis ustulus, one of the species harvested for salep and illustrating a pair of tubers, and a tourist site photograph of Turkish dondurma.