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...]

Tuesday, 19 April 2016

Giant daisy succumbs to Robinson Crusoe's goats


I saw a humming bird in Chile once. It hummed by as I peered into the flower of a Chilean Chilean Bellflower (Lapageria rosea). Both were in the garden of Hotel Antumalal in Pucón where I was staying on my way to see Monkey Puzzle Trees in the shadow of the smoking Villarica Volcano.

Still, enough bragging about humming birds (one), Chilean wild flowers (in a garden) and latent danger (it was weeks since the last eruption...). What I didn't see - in a garden or in the wild - was the Robinson Crusoe Island Cabbage Tree and its humming bird pollinator. Now that would have been a story to tell.

Dendroseris litoralis is not so rare in cultivation but you have to travel to Robinson Crusoe Island in the Juan Fernández Islands archipelago, about 600 kilometres off the coast of Chile, to see it in the wild. This big-leaved daisy has been described as 'amongst the rarest plant species in the world', threatened by habitat distruction and feral goat grazing.



With its large rubbery leaves, the Robinson Crusoe Island Cabbage Tree looks a bit like some of the giant thistles (Sonchus species) on the Canary Islands, having adapted to a similar island environment.  It's a woody, fast-growing plant. This specimen in our nursery grew from a seedling donated just a few years ago by local grower and collector Alistair Watt.


Robinson Crusoe Island is named after the famous Daniel Defoe character who was shipwrecked on an island for 28 years, at first alone and later with his friend Friday. This particular island in the Juan Fernández Islands was where a real life sailor, Alexander Selkirk, was marooned for five years in the early eighteenth century. According to Wikipedia, the Chilean government changed the islands name from Más a Tierra to Robinson Crusoe in 1966, to 'reflect the literary lore associated with the island and to lure tourists'.

Robinson Crusoe Island is home to other botanical oddities, such as the Chonta Palm (Juania australis), and seems to be worth adding to your bucket list if you like botanically bizarre island floras (along with Socotra, Canary, New Caledonia...)

Until recently the Cabbage Tree was reduced only a few individuals on the island but propagation in gardens and, I'm assuming some reintroduction in its native habitat, have tipped the balance a little. However it is still consider critically endangered in the wild.

Although it has been shown that hummingbirds are the most likely pollinator (attracted by its sugary nectar), it doesn't actually need them. Along with about half the world's plants, this particular species of Dendroseris is what we call 'self-compatible'. That is, it can set seed without pollen from another individual. This makes it a perfect plant for gardens but perhaps not adaptable enough in the wild (cross breeding allows the mixing of genes and generally better ability to adapt to change).

In Daniel Defoe's novel, Robinson Crusoe survives with the help of a few crops, his bible and some goats. On Crusoe's namesake island it is the goats that are the undoing of the Cabbage Tree. That and the 800 or so extra humans.


Images: the plant in the Melbourne Gardens nursery, 18 December 2015.

Tuesday, 12 April 2016

Good health from a happy tree in a wise location


It's a happy person that doesn't have cancer. And it's a Happy Tree that might provide one of the cures for cancers.

Camtothecin was discovered by western medicine in the 1950s, when it was extracted from what we call the Happy Tree, from the Chinese name Xi Shu. Botanically it's known as Camtotheca acuminata, one of two species in the genus Camtotheca - a name that translates as 'curved sheath', a possible reference to the miniature banana-like fruits.


The tree is native to southern China and Tibet, but nowadays at least uncommon in nature. Seed from one of the remaining 4000 trees was collected from Yunnan Province about 20 years ago by our Curator of Chinese Collections, Terry Smyth.

According to a 2011 report by the Rural Industries Research and Development Corporation (RIRDC), demand for this chemical worldwide is estimated to require at least 100 million trees. So we need to grow more than 99,996,000. We have nine growing in Melbourne Gardens, all sourced from the seed collected by Terry.

The tree is described in the report as 'easy to grow in Australia' but does need a good source of moisture. One of our Senior Curators, and water guru, Peter Symes thinks the tree I've photographed here has done so well because of its roots are sourcing moisture from the lake. Colleague Steven Liu, who grew up in China, says it seems to grow better here than in its home country.

As you can see in the top photograph, this particular tree (the tall one) was planted next to the William Tell Rest House. This structure is a miniature version of a similarly named chapel in Lucerne, Switzerland. I don't know of any particular resonance with the Melbourne Gardens but happily, according to the 15th century legend, William Tell's arrow splits the apple on top of a nobleman's son's head and so lived to have his tale told.


These are the first pictures of the first flowering of our Happy Tree. The flowers are in a head, like a pom pom, with the male parts (stamens) prominent. If you look closely you can some tiny lime-green blobs on the spongy surface of the female centre of each flower; this is where the pollen from another flower needs to land.The flower without stamens in the top picture is older and, if fertilised, on its way to producing a cluster of scimitar-shaped fruits. As Terry says, 'the globular flowers are interesting but not particularly beautiful' (they are certainly high in the tree and difficult to photograph).

But chemicals in its stem and bark are worth celebrating. While you here plenty of reports of cancer-curing plants, camptothecin has been described as 'the most promising anti-cancer drug ... ever ...found'. It is one a range of drugs that inhibits chemical reactions inside the body leading to reduced tumor growth.

Its complicated chemical structure makes it hard to synthesise in the laboratory, so the main source of the drug is still the Happy Tree (although there are side effects from this drug which artificial preparations may be able to minimise). The market for camptothecin in 2004 was worth a billion US dollars.

The 2011 study concludes that the tree is fast growing and suited to warm, humid regions of Australia such as coastal Queensland. So while there might not be potential for a Victorian industry, we can grow and marvel at this tree in our gardens if we plant wisely.

Planting wisely is how we intend to adapt to climate change at the Melbourne Gardens. Sometimes it means planting new kinds of plants, but it also means thinking about where and how we plant trees, taking best advantage of nooks and crannies such as this idyllic lakeside setting.

Like the Handkerchief Tree of two weeks ago, this odd plant used to be in the family Nyssaceae but is now included in the dogwood family, Cornaceae. In leaf it's not unlike Cornus I guess. In a 2007 piece written for Dave's Garden Jeremy Lucas compares the leaves to those of an avocado, but with 'heavier, pleated veining'. That seems about right.  


Jeremy Lucas tried to track down why it was called Xi Shu (Happy Tree) in China but didn't get a definitive answer. Perhaps it is due to its tall, handsome stature and bright green leaves. Alternatively, as I thought when I started writing this and as a Chinese correspondent suggested to Lucas, the happiness may be related to curing disease, given it has long been a medicinal tree in China.

And if that doesn't satisfy you, track down the apocryphal story on ChinaHorticulture.net. I don't get it but the legend starts with a thing called Desperate Grass in the Garden of Eden, and ends with singing trees on a desert island. God plays a major role, and Adam and Eve bit parts, but the plants really star. In the end, the singing trees are given the name Happy Trees because wind blowing through them makes a similar (pleasing) sound to wind through the exiled Desperate Grass. Everyone, except perhaps Adam and Eve, are happy.

Note: We featured this tree on Instagram (@royalbotanicgardensvic) and our Royal Botanic Gardens Victoria Facebook page on 28 January 2016, but it's worth (William) telling more of its story and publishing a few more images (all taken the week afterwards). The picture of the banana-like fruits near the top of the post is an exception; it comes from the website ChinaHorticulture.netThis is what our's looked like in mid-February, on their way to pseudobananadom:


Tuesday, 5 April 2016

The somewhat immortal House Leek at work 24/7


In leaf this plant looks so ordinary, so familiar, we barely notice it. But when it sends up this chunky stalk topped with an umbrella of, if not showy, at least curious flowers, you take a second look. I did.

What we have here is a succulent called Sempervivum, probably Sempervivum tectorum. You see it, or one of its relative, all over the place. It's in the family Crassulaceae, which includes fleshy leaved plants, often with leaves tightly packed in a rosette, like this one. The flowers most often rise above the rosette on some kind of stalk.


Sometime ago I promised to blog about Crassulacean Acid Metabolism, or CAM. Many, if not all, members of the Crassulaceae exhibit this special way of converting sunlight into food (photosynthesis). So too do other plants such as fleshy orchids and bromeliads - it's an adaptation to living in places or climates where water is scarce, such as deserts and up in trees.

The basic concept is that the (usually fleshy) leaves and stems act like a battery, capturing carbon dioxide at night when it's safe to open the pores (stomata) in the leaf. The carbon dioxide is combined into a chemical call malate, which can be stored inside the cell (actually in the 'vacuole'). The plant then strips carbon dioxide from the malate during the day - when the sun's energy is available - to build the sugars needed by the plant to live and grow.

The benefit to the plant of this time shift in the two parts of photosynthesis (other plants take up and fix carbon dioxide during the day) is less water lost during the day. Opening your pores to take in carbon dioxide is always a compromise in a hot, dry environment since water will be lost through evaporation.

So our Sempervivum is adapted to life with limited water. In our garden it gets plenty but it does mean that we can forget to water it occasionally, or take a holiday and return to find it alive. This accounts for one of its common names, Live Forever. In fact it's botanical name means the same thing: always alive.

Yet while the plant as a whole may always be alive, once a rosette flowers, after a year or two, it dies. By that time there will be plenty of offsets around the base so the thing lives on*.


If this species is indeed Sempervivum tectorum, we have access to more obscure common name. Tectorum means 'of roofs', and according to Wikipedia, this species (and quite possibly others) were apparently planted on the top of houses to 'ward off fire and lightening strikes'. This is celebrated in the common name House Leek (note the spelling, and therefore reference to the onion relative it might resemble a little in flower rather than holes in the roof).  There are also other names such as Jupiter's Beard that may relate to the plants connection with thunder and storms, in a good way.

If you look closely at the flowers in my pictures you can see they in their 'male phase' with active stamens producing pollen but the female bits curled up and non-receptive. This way the plant is more likely to avoid self-pollination, a topic I seem to return to quite often in this blog (e.g. the Monkey Flower). You can also see there are lots of floral parts - a dozen or so petals, about twice as many stamens and who I reckon a dozen female bits. Plenty going on, day or night.


*Or so the theory goes. As it happens, a month or two after taking these pictures, our entire clump has succumbed. Bad botany or bad plant husbandry? 

Tuesday, 29 March 2016

Handkerchief tree in full blow


Appropriately, as Christians and others celebrate Easter, today my talking plant celebrates Père (Father) Armand David, a missionary who himself became converted - to become a naturalist - during his time in China. He was the first European to 'discover' the Giant Panda and has numerous animals and plants named after him. The plant most often associated with his name is the Dove Tree or Handkerchief Tree, Davidia involucrata.

Jane Kilpatrick tells his story, and that of other European missionaries who botanised in China, in her recent (2014) book Fathers of Botany. David was born in the south-west of France in 1826 and Kilpatrick says he credits his Basque upbringing for his stamina.

The Dove Tree was found by David in 1869, in the Baozing County of Sichuan Province in central China, where he also found the Giant Panda. Both live in mountain forests, the Dove Tree between 1100 and 2600 meters above sea level.


The flowers are small and clustered together, but like a few other plants I've mentioned, they are associated with large showy 'bracts'. There are two bracts in this case, each resembling a handkerchief or something more romantic. Irish botanist Augustine Henry saw a single tree in flower in 1888 and says it was 'one of the strangest sights… a solitary tree of davidia in full blow…waving its innumerable ghost handkerchiefs'.

A decade later, noted English plant collector, E.H. Wilson, described the bracts blowing the breeze as resembling 'huge butterflies or small doves hovering among the trees'. In fact it's said (Seamus O'Brien, In the Footsteps of Augustine Henry and his Chinese plant collectors) that to see this plant in nature was the sole reason Wilson made his first visit to China.

The first illustrations of the flowers were from pressed, dried specimens, and the bracts were shown sticking upwards. In fact, of course, they flutter downwards like someone waving a white handkerchief.

You'd think these bracts have something to do with attracting pollinators to the inconspicuous flowers, although perhaps not biped mammals. The Arnold Arboretum in the USA has helpfully done the research, concluding that the bracts are part umbrella (shielding the flowers to keep pollen dry) and partly sex appeal (attracting insect pollinators). They even help support the tree when young, producing sugars from sunlight (photosynthesis), before they turn from green to white.



This is an odd plant, often classified with the Tupelo, Nyssa sylvatica, and Happy Tree (more on the latter in two weeks time...), in the family Nyssaceae. (The Tupelo has beautiful autumn colour, always attracting attention in April in the Melbourne Gardens.) In the past the Dove Tree has been also placed in its own family, the Davidiaceae, but the latest molecular classifications include the family Nyssaceae within an expanded Cornaceae (some species of which have four large petal-like bracts around the flowers, not dissimilar and often as striking as the Dove Tree flowers).

Henry (and no I don't know why all the surnames can double as first names) had actually found a new variety of the Dove or Hankerchief Tree, later named vilmoriniana. It had smooth, hairless leaves (apart from a few hairs on the under surface of the veins) compared with the downy under surface of the leaves collected by David. This variety is now the most common in cultivation, particularly in cooler regions.


While we don't distinguish on our census what variety we have in Melbourne Gardens, the leaves of the one specimen I could find don't have a hairy under surface so I'm presuming they belong to variety vilmoriniana. And if I enlarge the pictures I took in the garden of Tieve Tara, at Mount Macedon, in October 2014 (adorning this post), again I don't see any overt hairiness.

That's settled then. We can now just enjoy the flowers in full blow.


Tuesday, 22 March 2016

Hot on the trail of excess petals in the Bishop's Hat


And while we are counting petals (see last week's post) I have another corollic conundrum (assuming you'll allow me to use the term 'corollic' as an adjective for things pertaining to the corolla, the collection of petals in a flower). It relates to our latest chilli plants, gifted to us by Neville Walsh, and in flower here in the middle of January.


The plants are rather tall for a chilli, getting up to two metres or so (ours only hit one metre), with a fruit that is unusually shaped - like cap of some kind (but more of that later) - and flavoured - the basal part is relatively mild but sweet, but the top carries a decent (but not overwhelming) punch.

Tracking down the correct name for this chilli was, as it is for lots of garden favourites, tiresome. I think I have it sorted now though, thanks mostly to a Suburban Tomato post and to Natureman, responding on the UBC Botanical Garden Forum.

What I'm illustrating here is what we often call Scotch Bonnet in Australia, but elsewhere and sometimes in Australia too, Bishop's Hat, Bishop's Cap or Bishop's Crown. Scotch Bonnet in the UK, as I can attest from a particularly volatile sauce I bought from a Brighton (UK) chilli shop a few years back, is a quite different thing: it's a very hot fruited cultivar of Capsicum chinense, the same species responsible for the habaneros. Our fruit gets eaten by possums when red and ripe (yes a strange thing for us to do, grow food solely for wildlife), but here they are juvenile and green on the last day of January (two weeks after the flower photos).


The Australian Scotch Bonnet, or universal Bishop's Hat, is a cultivar of the species Capsicum baccatum, even though occasionally you see it referred to Capsicum annum. These two species are easily separated if you have flowers: those of baccatum have yellow or green spots, those of annum (and for that matter chinense) are entirely white or off-white.

So with its spotted flowers and bonnet/hat-shaped fruits that are not overwhelmingly hot in flavour, our cultivar belongs to Capsicum baccatum a South American species. Wikipedia agrees and says it's a cultivar of variety pendulum, providing a few more common names, such as peri peri (although not the 'real', and again hotter, peri peri which is a cultivar of year another species, Capsicum frutescens, another entirely white-flowered species).

According to a key at Jungle Rain the varieties are distinguish on the basis of their flower spot colour, yellow for variety pendulum and pale green for variety baccatum. Our plant has flowers with spots that could be described as either colour really so I'll stick with the straight species assignation. All up, tiresome to untangle but reasonably reasonable.


On the other hand, the number of petals on each flower seems entirely unreasonable. On our bush at home there are five, six or seven, in relatively equal proportion. I thought Capsicum, like all members of the family Solanaceae (think potatoes, tomatoes, Deadly Nightshade and Kangaroo Apple), had five petals. Here for reference is the flower of a Thai Birdseye chilli plant from last year, with five, entirely white petals (a cultivar of Capsicum annum).


When I checked a reliable sources (such as Vernon Heywood's majestic Flowering Plant Families of the World and David Mabberley's The Plant-Book) I find that while five is the most usual number of petals in a plant of this family, they do vary: Heywood says four to ten, Mabberley four to six.

Well, our flowers have five to seven petals. I can't recall ever seeming more than five on the entirely white-flowers species of Capsicum we've grown before, or for that matter on tomatoes or potatoes. But then again, I wasn't really looking, until now.


Notes: Lynda Entwisle noticed and commented on the odd (and even and odd) number of petals on these flowers, prompting this post. All pictures are from our backyard (the single picture of a white-flowered Thai Birdseye is from a couple of years ago, with the Bishop's Hat flowers and green fruit from January this year).

And a bonus picture, of a fruit picked green and reddened up inside, photographed a couple of weeks ago...