Tuesday, 21 June 2016

Gourds of two sizes needed for Papuan heath

This rather exotic heath, with flowers and fruits like a pumped-up blueberry, is four years old. It was propagated from a cutting by our nursery horticulturist Dermot Molloy. Until a month or so ago we hadn't confirmed its species name, although we knew it was a Papua New Guinean member of the heath family and, we were pretty sure, in the genus Dimorphanthera.

[Nearby in the nursery we have Macleania ruprestris, in the same family but from Chile, also with chunky bell-like flowers followed by a succulent berry. It's in berry at the moment - pictured to the side here - with some very small flower buds appearing at the branch tips. So with two species, we have the making of a fascinating collection!]

There are (or at least were in 2003) 87 species of Dimorphanthera, most of them native to New Guinea or nearby, a region that might be described as eastern Malesia. They are shrubs, small trees or sometimes lianas, but no matter their life form, they tend to climb or drape themselves over other plants. Those plants include relatives in the heath family Ericaceae, such as Rhododendron and a genus more similar to Dimorphanthera, Vaccinium (including species that gives us cranberries and blueberries).

Now, let's tease one of those flowers apart...

The name 'dimorpho-anthera' refers to the flowers having two different kinds of anthers, the pollen-bearing male bits. Typically half of these almost woody anthers are bigger than the other half. In the flower I pealed open the anthers all looked pretty much the same but they tend to be in pairs with one longer than the other and with the green bit extending beyond the brown strips either double or singly pointed (most obvious in the bottom two in the picture above).

Apparently such an arrangement is an attractive, or at least productive (for the plant), proposition for visiting birds, which seem to be the targeted pollinators. Mostly I suspect they are just curious about what's inside the fleshy, porcelain-coloured tube.

Our first Director, Ferdinand von Mueller, devised and applied the name 'Dimorphanthera' to this group of plants, firstly in 1886 as a subgenus of Agapetes (although not adequately, and a later author, Carl Georg Oscar Drude had to rectify it to meet the needs of botanical nomenclature).

In 1890 (above), Mueller raised Dimorphanthera to genus level in the second volume of his notes on Papuan plants, again rather ineffectively (you see various renderings of the 'authorities' for this name, including Johannes Jacobus Smith as fixing up Mueller's genus name attempt).

So that's the genus. Our horticultural botanist, Roger Spencer, has now confirmed the genus and given it a species name: Dimorphanthera alpina. The shape of the green calyx at the base of the flower, the size of all the floral parts and the colour of the floral tube (the fused petals) all match this species. As do the rather cryptic black spots on the edge of the leaf, which you can (just) see in the following picture (along with an unopened flower bud). Roger confirmed these spots are actually small teeth, slightly embedded into the leaf margin.

To grow Dimorphanthera alpina it seems best to treat it like a Vireya Rhododendron, providing good drainage and protection from extreme cold (frosts). Although from the tropics, as its name suggests it grows at higher altitudes and will tolerate night temperatures down to around 10 degrees C. Like others in the family (e.g. Rhododendron) it likes acidic soils.

Royal Botanic Gardens Edinburgh has an extensive collection of Dimorphanthera, with 19 'taxa' (species, and categories below species like subspecies, varieties and forms) growing in 2012. Elsewhere it's not a widely grown genus. It should be.

Tuesday, 14 June 2016

Xocolatl! Presumed goat droppings make good god food

Sydney's newest botanical attraction, The Calyx, opened on Saturday, starring Theobroma cacao and its popular products. Lindt is a beneficiary of the products (and a sponsor) giving you a hint about what's inside these yellowish fruits.

(If you want to experience the construction of The Calyx in time-lapse, or see it the way a drone does, talk a look at these videos.)

Theobroma is Latin for 'food of the gods' and those gods were or are presumably those of the Aztecs. Native to tropical America, the Cocoa Tree was called Xocolatl by the Aztecs, meaning bitter water. From Xocolatl we get the species name cacao and our own common names for the crushed beans, Cocoa and Chocolate.

Surprisingly, perhaps, Theobroma is in the mallow family, Malvaceae, with things like hibiscus and cotton. Still, you also find tucked into this family odd things like kapok and durian. There are 21 other species of Theobroma, including one with fruits that are juiced in South America. But chocolate is the main reason you are familiar with the genus.

Chocolate can be good for you, as the possum in the nest above will attest. It's said that eating a little a day - 46-105 grams - can help lower blood pressure. The cocoa seeds have also been used to treat various ailments, including heart disease, in humans.

Mostly we eat the dried and fermented seeds of the Cocoa Tree (which we then call cocoa beans) because they taste good. I like mine with just a little sugar: 70% cocoa, in the 'bittersweet' range in the US, is my preference.

About 30 to 40 of these seeds are produced inside a large yellow, to red or orange, fruit (see top of post) that looks like the Beatles' Yellow Submarine or perhaps a pointy egg. Technically it's a berry but generally referred to as a pod.

Before it fruit, the plant flowers. The flowers erupt out of the stem, something you find in a few tropical plants and which we like to call cauliflory.

According to Royal Botanic Gardens Kew, fruits in the wild are pollinated by midges. In our glasshouses - and the pictures above were taken from the Palm House at Kew Gardens as well as the The Calyx in Sydney - hand pollination is needed. Although ants do help out at Kew Gardens, and there is some kind of blurry midge/fly in the bottom right of the first picture!

Dale Dixon, Curator Manager of Royal Botanic Garden Sydney, says they are struggling to get any viable fruit in the Calyx plants. The small success below, on one of their trees, seems to have aborted before full development.

Even in nature it seems a very small percentage (5% says Kew) of the flowers produce fruit, so there must be constraints on pollination to do with timing the various bits and pieces maturing, or some kind of incompatibility, all to encourage fewer but more 'productive' crossings. The fruits are big so the Cocoa Tree has a strategy of doing what it does well rather than lots of it.

The fresh seeds are covered in a white pulp which discolours to brown when the seeds are dried and fermented (by sun if you have it). You can read elsewhere about the history of chocolate in Europe, and the excitement of discovering that sugar makes it taste better, but let's just say after a slow start when Christopher Columbus disregarded what looked like goat droppings on a canoe, it took off.

Images: Outdoor trees from Xishuangbanna Tropical Flower and Plant Garden in China, cluster of flowers from Palm House at Kew Gardens, Easter egg nest and squirrel at Kew Gardens, and the rest from The Calyx and nearby (thanks to Dale Dixon and Jimmy Turner for a pre-opening tour). Thanks too to the Royal Botanic Gardens Kew webpage on Theobroma, which is where all the interesting information comes from. To hear more about The Calyx itself, listen to my interview with Dale Dixon for ABC RN's Blueprint for Living. And this is Dale examining the flower of Theobroma cacao...

Tuesday, 7 June 2016

New Guinean rhododendron a secret no longer

On the weekend I posted a picture of a big, white, vireya rhododendron flower on my Facebook page, dutifully tweeting it and 140 letters of explanation to the Twitterverse. Instagram? Nuh. Snapchat? I forgot about that the day after I joined. So old school social media.

This striking bloom is worth more than a glancing mention on social media. It deserves a ... blog post! Which, through my primitive automated social media marketing, will see it reappear on both Facebook and Twitter (and debut in the more stately rooms of LinkedIn). Still, it's worth a second glance.

The name of this plant is Rhododendron x husteinii. Now. Back in 1989, when Lyn Craven and John Rouse published their paper on its discovery, it was called Rhododendron leucogigas 'Hunstein's Secret'. You can read all about it in the Journal of the American Rhododendron Society, or rely on my potted version below.

Lyn Craven, botanist at Canberra's Australian National Herbarium for more than 30 years, began his scientific career in the plant taxonomy unit of the New Guinea Survey Group of CSIRO. He studied horticulture at Burnley Horticultural College (now part of University of Melbourne) and worked in the Parks and Gardens Branch in Canberra before settling into his position as the Herbarium.

John Rouse was a physicist as well as enthusiastic collector and grower of rhododendrons, publishing over 70 papers on their cultivation and biology. Rhododendron rousei 'John Rouse' seems to have been very much named after him! As a trustee of the Baker Foundation, he was instrumental, along with Director Phil Moors, in setting up our Australian Research Centre for Urban Ecology in 1998. He also sat on the Advisory Committee of the Maud Gibson Trust, another great supporter of the Royal Botanic Gardens Victoria.

His son Andrew Rouse continues in his horticultural footsteps, growing all kinds of rhododendrons in his backyard and small glasshouse in the inner east of suburban Melbourne. Andrew also volunteers at the Rhododendron Garden in Olinda, creating the rhododendron display inside their new glasshouse. The picture above, my social media image, is from his home glasshouse, taken on Saturday (4 June).

Now back to our secretive plant from Mount Hustein. While in Papua New Guinea in August 1966, Lyn Craven found a small seedling 'growing on a branch fallen from the forest canopy' in rainforest at 1200 metres above sea level on Mount Hunstein, in the East Sepik Province. There was only one small individual and enough material for a single cutting. The plant had large leaves but no flowers, and was tentatively assigned to species known from the region, Rhododendron schlechteri.

That cutting was sent to Melbourne where it was successfully propagated, presumably by John Rouse. When it bloomed (illustrated above, from the 1989 journal article), the large white flowers - 12 cm long and 12 cm wide - were more like another species, Rhododendron konori or its presumed cultivar/hybrid Rhododendron 'Gardenia'). However the fine detail of the plant, including the scales on the leaves, shifted its allegiance to a species called Rhododendron leucogigas (a species name very appropriately meaning 'white giant'). known only from the Cycloop Mountains in Irian Jaya.

The Mount Hunstein collection was thought worthy of its own cultivar name - 'Hunstein's Secret' - suggesting it was not exactly the same as the form found in Irian Jaya.

There is a tendency for westerners to misuse the word 'discover' but Craven and Rouse suggest that few if any humans would have seen this plant. The area is not settled and local nomads, at least after the 1960s, stick mostly to the rivers rather than high mountains.

The name Rhododendron x hunsteinii was published last year by George Argent from Royal Botanic Gardens Edinburgh, in the second edition of his Rhododendrons of the Genus Vireya. I haven't seen the book but I'm told by Andrew Rouse that molecular sequencing confirmed it is a hybrid between Rhododendron leucogigas and another species. Andrew did note on Saturday that 'it may well be a distinct species'. His flowering plant was struck from a cutting in 2004 and last flowered in 2009 - the beautiful picture at the top of the post was taken by Andrew then.

[I wouldn't normally include such an out-of-focus image but here is Andrew Rouse, to the right of Michael Hare, Convener of the Growing Friends Group, Melbourne Friends, Royal Botanic Gardens Victoria. Let's just say it was dark and misty, and the instability of my phone camera adds to the intrigue.]

Tuesday, 31 May 2016

The last waterwheels of death?

As regular readers would know, every now and then I come across a plant so compelling I feel obliged to tell its story without ever having laid eyes on it. Today it's a relative of the Sundew (Drosera) called Aldrovanda vesiculosa.

The common name - Waterwheel Plant - caught my attention. I'd just been listening to the Science Show on ABC Radio National, getting the latest on how bacteria evolved their motorised flagella and I though perhaps here was a flowering plant able to spin like a wheel.

It isn't and it doesn't, but what a plant. It consists of a floating stem with traps extending out like a water wheel. These traps work in a similar way to those of the Venus Flytrap, Dionaea muscipula, snapping shut in 1/50 of a second when an insect visitor to trips two hairs in the mature device. Charles Darwin called it the 'miniature aquatic Dionaea'.

There are lots of species of Aldrovanda in the fossil record, but only one living on Earth today. This species, Aldrovanda vesiculosa, has been recorded from Australia, Asia, Europe and Africa. Records are scatted and the species is considered to be at risk of extinction worldwide.

The map of its distribution in Australia shows a species of apparently no particular preference other than aquatic habitats more or less near the coast. It's in the north, the south and even in the south-west - but not (yet) found in Victoria or Tasmania.

As reported by Robin Wylie in New Scientist, habitat destruction and illegal collection (hence the vagueness in locality reports on the web) have meant it is down to 10% of its abundance a hundred years ago. In NSW there is a 'Saving our Species' page dedicated to its survival. There are three existing localities mapped and a fourth site flagged for relocation.

Relocation depends on gathering, storing and germinating seed, and that's yet another problem for the species (outlined in a recent paper in the Botanical Journal of the Linnean Society). A group of mostly Western Australian researchers led by Adam Cross found that only 12% of seeds could be germinated after one year. Most of them succumb to fungal attack.

The seed coat looks smooth but according to this report it has a 'honeycomb-like arrangement' which helps the seed to float but also provides an easy route for fungi to enter the seed.

Freezing kills the seed but cryostorage of actual plants or embryos may be possible. For now though, the authors suggests we protect their habitats and put more effort into finding out what stops Waterwheel Plant thriving in nature.

The Waterwheel Plant is the only aquatic plant with a trap that snaps shut to capture prey. In 1876 Charles Darwin thought this was pretty cool, and went on to show it digested water fleas and mosquito larvae. Unless we care for this plant in the wild, and support some conservation science, a mere (in evolutionary terms) 140 years later we may be witnessing the end of this strange and beguiling plant lineage.

Images: Having not seen this plant myself, these images are not mine. The top two are from Summa Gallicana, the top one originally sourced it seems from Barry Rice's sarracenia.com (who allows the use of his images subject to attribution). The close up of the 'waterwheels' thanks to Lubomir Adamec, from the US Geological Survey. While all the plants illustrated here are quite green, in Australia the Waterwheel Plant is usually reddish in colour, not unlike many of the sundews. Here is another photo by Lubomir Adamec (Carnivorous Plants) of a plant from northern Australia.

Tuesday, 24 May 2016

Rare redwood at dawn

Some time ago a reader, Rob Dabal, encouraged me to write more on plants in the Royal Botanic Gardens Victoria collection that are extinct in the wild, or nearly so. Rob was responding to a post on my South American botanic garden trip where I mentioned (in passing) the extremely rare Easter Island pea, Sophora toromiro.

I've already provided some background to the Ginkgo or Maidenhair Tree, Ginko biloba, now either extinct in the wild or represented outside gardens by a few trees in China. And much has been written about the Wollemi Pine, Wollemia nobilis, and the discovery of 100 or so trees north of Sydney in 1994.

The Dawn Redwood, Metasequoia glyptostroboides, is worth a separate post. It's also timely, as we head towards the end of autumn. The Dawn Redwood is one of a handful of conifers (pine relatives) that looses its leaves for winter. That is, it's deciduous (as is its close relative, the Montezuma Bald Cypress, Taxodium distichum, one of which is our tallest tree in Melbourne Gardens).

We have two specimens of Dawn Redwood in Melbourne Gardens, one in about the middle of Eastern Lawn (the big expanse of grass dotted with trees and those fantastic forked Grass Trees), the other (photographed here) near to Gardens House and the perennial border. The image at the top was taken last week, at dawn. This next one in early April, later in the day.

It's a tree you'll find all over the world in botanic gardens, and some major parks and even private gardens, but it's extremely rare in its native habitat, now persisting in only a few small stands. Unlike the ginkgo, we are confident the Dawn Redwood has maintained this foothold (roothold?) without human intervention, although now it's human rice cultivation in addition to poor reproductive success that threatens its survival in 'nature'. 

The story of the Dawn Redwood is very similar to that of the Wollemi Pine in that it was known from the fossil record and thought to be extinct until a small population was brought to the attention of the scientific community. In the case of the Dawn Redwood it was a young forester, Wang Zhan, who made the first botanical collection, in 1943 (branches of the Wollemi Pine were first collected by a Park ranger, David Noble, in 1996).

The tree was well known, and respected, by the local village who had erected a simple temple in its honour. We now know there are a number of small populations near the border of Hubei and Sichuan provinces in western-central China. Both the Wollemi Pine and the Dawn Redwood were rushed into cultivation, first in botanic gardens and public parks, and then a few years later commercially. 

According to our horticultural historian, Roger Spencer, seed arrived at Royal Botanic Gardens Victoria in 1947, and the first trees were seven metres tall by 1961. The two alive today I presume came from that original batch, so the one photographed here near Gardens House (above again in early April) could be just under 70 years old (although it looks younger than the other). It's probably 20 metres tall.

Like the Wollemi Pine there is only one species of Metasequoia extant today. I gather the common name 'Dawn Redwood' is actually an oblique reference to its fossil record, and it's presence at the 'dawn' of conifer time. It's commonly thought to be a simple reference to the red-bronze foliage at this time of year. I like to think of it as recognition of the time of day when Wang's first saw his tree, at dawn, on 21 July 1943.

While superficially like the Coast Redwood (Sequoia sempervirens) and Giant Redwood (Sequoiadendron giganteum), and other members of the Taxodiaceae family (including, more closely, the Montequma Bald Cypress) it can be distinguished by the deciduous leaves arising opposite one another from the stem in a feather-like arrangement. Reminiscent in fact of our Wollemi Pine.

Like the Wollemi Pine, it has separate female and male cones. These next photos (taken just after dawn in mid April, as the leaves were turning) show the ladies first. The female cones were higher in the tree, like the Wollemi Pine...

Also like the Wollemi Pine, we grow this species in our gardens, and particularly in botanic gardens, to preserve the species. At the same time we encourage conservation in its native habitat, so that all the organisms that depend on this tree and the tree depends on itself, can survive the human epoch.

Tuesday, 17 May 2016

A tree to take your breath away, literally

There are some ailments you don't mind having. For example if Tim Entwisle was suffering from illeism he wouldn't care. Or gratuitousness for that matter.

More botanically, Richard Mabey (in his Cabaret of Plants) diagnoses the wife of our Governor of Victoria, Lady Barkly, as having pteridomania. The prime symptom being a frock festooned with fern motifs worn in 1860. This kind of enthusiasm for ferns won't kill you, but you should avoid eating bracken and watch for unstable Bird's Nest Ferns in the canopy above.

Plenty of flowering plants are bad for your health. You are probably aware of Deadly Nightshade, Hemlock and Mandrake. The hardy oleander is notoriously toxic, with the consumption of a few leaves said to be potentially fatal to young children. And then there are falling bunya pine cones, far more dangerous and likely than dislodged Bird's Nest Ferns.

File:Antiaris toxicaria 02.JPG

Last year, Royal Botanic Gardens Victoria horticulturist Stephen Lieu told us about a particularly poisonous plant, Antiaris toxicaria, with two evocative Chinese common names - See Blood Stop Breath and Seven Up, Eight Down, Nine No Life. More prosaically, it's also called the Upus Tree 
- 'upus' is a Javanese word for poison - or Poison Arrow Tree.

The botanical name, Antiaris toxicaria, also gives the game away. The genus name comes from 'Antjar', another Javanese word for this plant, and toxicaria from 'toxicon', a Greek word for arrow poison. The tree is native to Java, as you might have guessed, but also elsewhere in Asia through to tropical Australia and Africa.

So what kind of plant is this. It's a deciduous tree, with buttress roots, and drooping small branches, growing mostly in open grassy woodland across its range. Two of the African subspecies extend into wetter forests. There is only one species but up to five subspecies are recognised, three of them only in Africa I think. In Australia we have only subspecies macrophylla, with bigger leaves. 

It's in the fig family, Moraceae, so you'd expect a milky sap, and it's this sap the contains the rather nasty chemicals. Stories abound about its toxicity, most of them presumably apocryphal. The common name above with the incremental numerals refers to how many steps a 'victim' can take after consuming some of this deadly latex: seven steps up a hill, eight steps down or a full nine steps on level ground. Then you die. I don't know if See Blood Stop Breath adequately describes the symptoms of consumption, but you get the idea.

The Upus Tree has some literary notoriety too, featuring in the writings of Charles Darwin's grandfather, Erasmus Darwin, and the Russian poet Alexander Pushkin. You can track these down in all your favourite internet accumulators.

What doesn't kill you only makes you stronger of course. Recent research has focused on the chemicals found in Antiaris - gyocosides, prenylaurones, chalcones, flavenones, dihydrochalcones and the like - testing them for medical uses including tumor inhibitors.

Surprisingly the bright red fruit is quite edible to birds, bats, monkeys, antelope and us. Because some of the tall tales suggest you can't get within 25 kilometres of a tree without dropping dead, you might persuade a friend (or better still not a friend) to do the fruit picking and then make yourself a very nice jam without having to share it.

Images: This is one of those rare posts where I haven't seen the plant, and therefore definitely haven't photographed it. The drawing of the tree is from Stir Fry Central, and is said to be sourced (by Andrew Clifford) from C E Armand Semple, Elements of Materia Medica and Therapeutics figure 229, p 333. The leaves are from Wikimedia Commons, provided by Vinayaraj V R, and the sap leaking from an axe mark is from a PNG Trees page.

Tuesday, 10 May 2016

Brilliant salvia look-alike from Tanzania

The Uluguru Mountains of Tanzania are named after the local Luguru tribe, both of which are located in the middle-west of Africa, just south of the equator and east of the Congo, about a hundred kilometres from the Indian Ocean.

These mountains are best known for their wildlife - from odd sunbirds and shrews to rare frogs and millipedes - but it has an interesting flora as well. Over a hundred plant species are found only in the mountain range, most of them in the high-altitude (1200-2500 metres above sea level) rainforest.

Brillantaisia ulugurica, although named after the mountain range named after the tribe, is not restricted to just this area. extending elsewhere in Tanzania, as well as Democratic Republic of Congo, Rwanda, Burundi, Uganda, Malawi, Mozambique, Zambia and Zimbabwe. It seems to favour damp areas under or at the edge of tropical forests, and grows down to 700 metres above sea level. It's large floppy leaves suggest a moist, protected habitat.

It and other species of Brillantaisia (do take a look at my post* from Kew Gardens, about another species of this attractive genus) are often called Giant Salvia due to their big (up to 10 cm long), bold, salvia-like flowers. In fact they are classified in an entirely different family, the Acanthaceae (not the mint family Lamiaceae). The family Acanthaceae includes things like, well, Acanthus (Bear's Breach) itself, but also ThunbergiaJusticia, and these days even the mangrove genus Avicennia.

Most of the family Acanthaceae have leaves in opposite pairs that alternate at right angles to the pair below and above - what we call decussate. You can see this pattern in the plant from our Melbourne Nursery, in flower and photographed in January this year.

The flowers are of course the main attraction, for us and bees. It seems this genus is mostly bee-pollinated, with the two halves of the flower articulated to make sure the insect visitor comes into contact with the plants reproductive bits (thereby carrying pollen from one flower to another - generally a good thing...). I wonder with a big flower like this whether humming birds get into the act as well. Or maybe its left to the bigger bees, like bumble bees.

In this close up, you can see two elongate stamen-like things (carrying the anthers, with their pollen) sticking out the top. I understand flowers of Brillantaisia have two fertile stamens and two that are just for display (staminodes), and that the latter are deeper within the throat of the flower.

If you look at the top picture, though, you'll see the female receptive bit (style) way above the flower throat. There must be a bit of mechanical action going on when the bees visits the flower looking for nectar, bringing the style and the stamens closer to its body. I didn't think to dissect the flower or watch a bee visit when I took these pictures. I was simply overcome by the giant, purple blooms!

And in case you are wondering, the genus name has not an illiterate reference to these rather brilliant flowers, but commemorates a 19th century French botanist and explorer of west Africa, Brillant-Marion. As he may have discovered on his travels, other species of Brillantaisia are included in a local plant and snail concoction to treat small-pox. Although my source seems to be a little sceptical, noting that this was 'doubtless effective after the global eradication of smallpox in 1979'.

Note: Our specimen was kindly donated to the Royal Botanic Gardens Victorian by our friend and supporter, Meg Bentley. It's in our nursery at the moment but we hope to get it out into the public garden areas as soon as possible. 
*I wondered then, in that first post on this genus, where the name Giant Salvia came from. I know know - a different species!

Tuesday, 3 May 2016

Subtle colours in the proud Sydney sun

It was late summer in the inner west of Sydney, a week or two after the Mardi Gras but nobody told the street trees. There were crepe myrtles in vivid pink and purple, Tibouchina in that irridescent blue you only see otherwise in parades and festivals, and every now and then, bursting out from a tiny front yard, a giant pom-pom of ice-creamy frangipani.

So what does this Melburnian do in such an visually charged streetscape? I notice an odd form of the Coast or Sea Hibiscus. The yellow-flowered Hibiscus tiliaceus (also classified as Talipariti tiliaceum by some) is exotic and adventurous in its own way, travelling as it does around the world taking root on tropical and subtropical shores. My memories of it are from Borneo, some island off Queensland and Sydney's Royal Botanic Garden, but it is native to much of northern Australia and much of the pantropical world.

You can eat it, preferably wrapped around something else a little tastier, or eat off it (as a plate). In Australia I gather roots and shoots are eaten by Indigenous peoples in the north, and there are a range of medicinal benefits associated with the ingestion of leaves, bark and flowers - but as if often the case, on of those 'benefits' is as a laxative.

Now the flower in that top picture is clearly orange, not yellow. That's presumably because the flowers of the species open yellow in the morning and redden up later in the day. I only remember them as yellow, but perhaps that's because I tend to botanise idly in the mornings. This picture was around brunch time but perhaps they were yesterday's flowers.

The hint of red in the leaves, however, suggests a well-known cultivar. Hibiscus tiliaceus 'Rubra', sometimes called the Red or Bronze Cottonwood, is I think what grabbed my attention that steamy warm day in Sydney. My pictures were stolen glimpses as we walked past (not the high photographic art you are used to...) but it's a smart looking tree with deep green leaves with hints of bronze, and pale apricot orange flowers.

This cultivar does grow in Melbourne and we have a coppice of youngish plants in the [Rhododendron] Vireya Bed at Melbourne Gardens, near the Ornamental Lake east of the Rose Pavilion. There were not in flower in March (or now) but they look pretty enough in leaf. Sometimes you have to travel far away to appreciate what is close at hand, or some such glib saw.

Speaking of wood cutting devices, in a recent paper demonstrating how a brittle volcanic glass (obsidian) was used to make axe blades many thousands of years ago in Papua New Guinea, local craftsman used both Hibiscus tiliaceus and Hibiscus tiliaceus 'Rubra' to make a light but hard axe handle for a reconstructed archaeological tools. I'm not sure what this says about the origin of the cultivar 'Rubra' but perhaps it occurs naturally in this region.

To most of us the flower of the hibiscus is the attractant. I've blogged plenty of times about Hibiscus species, or its relatives in the family Malvaceae, and I'm being a little disingenuous saying they aren't Madi Gras standard. There flowers are hard to miss, and frequently bold and brash. It was just in this setting they were bystanders to the parade of pinks, purples and blues.

And rest assured my head is turned by flower colours in that spectrum. This is the shrub I photographed, with a small Jacaranda to its left. If that Jacaranda had been in full purple haze (or purple rain, if that's your thing) I wouldn't have taken a second glance at the Hibiscus.

Feedback: Lynda Newnam responded (3 May 2016) to this post on Facebook, noting that Cotton Tree gives it name to a beautiful spot in Maroochydore, Queensland, posting the following 'postcard':

Tuesday, 26 April 2016

Water Lily wavy for a day

Plants use flowers to attract pollinators. Sometimes they co-opt a nearby leaf or two to add to the allure, but mostly its the flower that does all the attracting. (There are of course plants that simply shed their pollen to the wind or water; their flowers tend to be less attractive, to us as much as other animals.)

Our experience with cut flowers is that they last for a few days to a few weeks. Attached to the plant we might expect them to last longer and in many cases (think of a rose or a camellia bloom) a single flower can be enjoyed for weeks. Sometimes, like the Moth Orchid (Phalaenopsis) they hang around for months.

Oddly, given all the energy needed and outcome required, there are flowers that last a day or two only. The Day Lily (Hemerocallis species) does what it says on the tin: the flowers open in the morning and start withering away that evening. The Titan Arum (Amorphophallus titanum) lasts an extra day, but for a flower structure that can be over two metres long and wide, that's a big investment for a 48-hour sexual display.

The flowers of the Yesterday Today and Tomorrow (Brunfelsia) last a few days, changing colour daily, as do the much showier flowers of the giant Victoria Lily (Victoria). Plenty of variation but our expectation, or at least mine, is that most flowers will hang around for a week at least. So when I noticed over summer the Wavy Marshwort (Nymphoides crenata) flowers vanishing overnight to appear next morning as pink buds like those above I assumed the Marshwort was just closing up its flowers to protect their delicate petals (I riff on this in my post on Shy Flowers).

Wary of making assumptions I decided to run an experiment. Neville Walsh and I tagged a couple of flowers with a knotted piece of vegetation. I didn't photograph them on that day, but here is what the flower looked like the next morning (it's the one on the left, with the loose garland).

The tagged flowers were all spent but in each case a fresh bud was sitting erect, right next to it. By mid-morning the bud was open and the old one hardly noticeable except to the experimental scientist.

We checked the next day too, just to make sure our first flowers hadn't been opened for days or weeks, with us tracking their last hours just by chance. Sure enough, the new flower withered in the evening, never to open again.

To the casual observer the pond looks more or less the same every day, for weeks on end. That is what the Wavy Marshwort does, at least at Melbourne Gardens.

[The astute blog observer will notice this last picture is taken on the same day as the image at the top of the post - my pictures of the next day were very unattractive. But take my word for it, at this scale the daubs of yellow looked pretty much the same the next day, and the next, and the next...]