Tuesday, 24 November 2015

West Australian heath a big inspiration

This is the Tassel Flower, yet another species you'll only find growing naturally in south-west Western Australia. It's not immediately obvious what kind of plant it is. I saw it growing on the forest flora near Beedelup Falls, thinking at first it was a weed of some kind.

Whether weed or native I struggled to put it into a genus or even a family. Before I saw the flowers I wondered it it might be some kind of bamboo or even palm. Even with flowers it didn't quite register with me at first. The flowers are small and I thought the petal-like parts might by in two whorls of three (i.e. six), making it perhaps a 'monocot' or lily of some kind.

Only when my wife Lynda, who complements my botanical knowledge well (i.e. often knows more than me!), said it looked a bit like the heaths you see in the Grampians did it twig (so to speak). I also recounted the floral bits finding them to be five rather than six.

Once in the right family, Ericaceae (in the part of this family that used to be Epacridaceae), I could easily track it down to Leucopogon verticillatus, the Tassel Flower. It's described in FloraBase as a 'bamboo-like shrub', so my first reactions were sound.

The flowers typically have a pink tube with the lobes white and bearded on the inside. The plants I photographed had flowers half strong pink/red and half pale, almost split down the middle, and presumably hairy inside (I have to confess I didn't look and its not obvious in my pictures). Leucopogon means 'white beard' and almost all species have flowers bearing tiny white hairs on their inside.

But it's an unusual looking heath and an unusual looking Leucopogon. At up to four metres high, the Tassel Flower is the largest Leucopogon species in Australia and the tallest epacrid (heath) in Western Australia. So it's a biggun.

The structure, with the long separated whorls of 'bamboo-like' leaves is also unusual. According to iNaturalist and plenty of other sites repeating the same line, it's distinctive form and similarity to bamboo made it the first Western Australian (plant?) export to Japan, for use in ikebana.

Engineers seem attracted similarly by its geometry. The design of the Tree Top Walk in the Valley of the Giants (a couple of hours south-east from Beedelup Falls) was apparently inspired in part by the Tassel Flower, with the pylon platforms (below) owing their form to this heath and the connections in between to a local sedge, Lepidosperma effusum.

Back in nature, it grows in Karri, Jarrah and Marri forests all evocatively named after the local Aboriginal words for the dominant eucalypts (Eucalyptus diversicolorEucalyptus marginata and Corymbia calophylla respectively).

Images: Apart from the Tree Top Walk pylon, which comes from the Donaldson+Warn website, all pictures are from Beedelup Falls, near Pemberton in south-west Western Australia. 

Tuesday, 17 November 2015

Trees of death

This post was written before the terrorist attacks in Paris and elsewhere, but it resonates a little with those acts of violence. Trees are a source of solace and stability in a sometimes hostile world, and I often wonder why there aren't more in our cemeteries. I also wonder why our cemeteries aren't more attractive places to visit.

A few months ago I was waiting in a cemetery in Newtown, in the heart of the inner west of Sydney, for Georgina Reid to arrive so we could talk about why she likes the Camperdown Memorial Rest Park (aka Cemetery).

Within minutes I was swooped by magpies and saw two Goths take in the funereal air. Later a mother gently dropped her daughter over a fence onto a grave stone. Locals walked past with their dogs, and a crew of gardeners (or were they weeders) bobbed around with their heads down and bums in the air. I didn't expect so much life in a cemetery.

Then again, this is an unusual burial ground. It was started in 1858 and closed 18 years later, overflowing with bodies and not the most pleasant of places to visit. The upside of all that was plenty of nutrients for the newly planted trees that are still with us.

Georgina Reid is a landscape designer and on-line magazine editor (The Planthunter) and she spoke to me of her daily dog walks through the cemetery, and of her sense that the trees and the body-ridden earth (my words not hers) are inexorably linked. You can read more of this in her own words in the article Cemeteries: Death and the Landscape.

This cemetery has stately oaks, Canary Island Date Palms and one giant Moreton Bay Fig. It also has patches of remnant Kangaroo Grass, among which the weeders I saw were presumably do all they could to encourage various local wildflowers.

Horticulture is now part of a progressive cemetery. Not all mind you. Georgina mentioned some new cemeteries that call themselves Memorial Parks but are anything but a park - they are devoid of any vegetation other than turf and a rose or two (plastic or real).

In Melbourne, the Greater Metropolitan Cemeteries Trust looks after 17 cemeteries and they have very publicly stated their intent to create places that people visit more often, to picnic or enjoy in a cafe. For the Trust, horticulture is as important as tombstones. Kew Cemetery (aka Boroondara General Cemetery), near me in Melbourne, is extremely proud of its trees and you can do a walk to locate them all, plus the interesting graves...

There are plenty of more adventurous projects or project ideas out there about how to more efficiently deal with our bodies once we die, and how to make that connection stronger between humans and the rest of the living world.

The Daily Mail reported earlier this year on the US Urban Death Project, where corpses would be placed in a 'giant tower' to decompose for about six weeks, after which they would have converted, more or less, to compost which would be either returned to families or 'spread in national parks'. I'm not sure that national parks need to spread compost but we get the general idea.

The Mail quotes research from the USA showing that it takes 90 thousand tons of steel, 9 million metres of hardwood and 1.6 million tons of concrete to bury the dead in that country alone. Cremation has come under fire for the amount of energy used to combust a body.

One of the advertising slogans for the Urban Death Project, which is crowd sourcing for funds, is 'eventually I'll be a lemon tree' (here the Australian male, in particular, notoriously contributes some of themselves to a lemon tree when the relieve themselves in the backyard). The Project argues that is is more than simply a method for turning our no longer needed bodies into plant food, but a better way to understand our place in the natural world.

In Australia, Living Legacy, led by Warren Roberts, is a fledgling program to combine the ashes of the dead with living forests. This particular concept is likely to be more about a spiritual and intellectual connection with the living world than fertilising it, but it too is part of a change in our attitude towards the dead. 

Trees in a cemetery, and trees that interfere (in the nicest way) with the plots, would seem to be a simple way to connect spent bodies with a world that continues beyond their life. We living can then enjoy those trees, and our cemeteries. 

Note: All images are from Camperdown Cemetery and my chat with Georgina will become part of the second series of Talking Plants 'the radio show', to run on RN over summer.

Tuesday, 10 November 2015

Black flowers provide bed and breakfast

As I said back in 2010, there are now black tulips, black roses, black violets, black hyacinths and, freshly created at that time, black petunias. Funnily enough, though, none of them are black. They are at best a rather darkish purple.

These were all bred artificially (that is, by us, the humans), seeking a flower that according to the hype at the time, would be intriguing, sexy and...something different.

I left out of that list some naturally occurring blackish flowers. The one you are mostly likely to encounter in Melbourne, although possibly not notice, is that of the New Zealand hedge plant Pittosporum tenuifolium. This is a commonly planted species, often in its variegated form (with white, silver or purple markings).

Although often sold as a cultivar called 'Nigricans', which means black, that name refers to the stems rather than the dark red or purple (blackish) flowers. In New Zealand this species is sometimes called the Black Matipo, which I like the sound of. Matipo is a name given to a range of different shrubs by the Maori and in this case it seems to refer to the wavy edges of the leaves.

The flower of the Black Matipo varies from purple through to what to all intents and purposes looked black or at least very deep red when I photographed this hedge in Hawthorn back in September.

A small blackish flower that is difficult for animals such as ourselves to see is an interesting evolutionary adaptation. Birds eat the fruits but, not surprisingly given their size, don't visit the flowers. Insects are usually implicated in pollination.

The flowers produce a honey-like perfume at night, which would normally be associated with a light coloured flower to attract moths. A prime example is our own Pittosporum undulatum, with its rich evening scent and very white flowers. Maybe the insects just stumble into the Black Matipo flowers, attracted solely by the heady perfume.

The best rationale I can find for dark coloured flowers is to provide a safe resting place, what is termed a 'protective shelter'. This argument has been used for the dark red or purple colour of some iris flowers.

Male solitary bees, in particular, are on the look out for places to rest overnight. So at the end of the day, when the Black Matipo flower is emitting its perfume, some insects will be out searching for a suitable rock or tree hollows where they can overnight. Popping out the next morning they will presumably carry pollen off to the next day's resting place, possibly another Black Matipo.

The male eucerine bees in the iris study don't visit the flowers at all during the day or at least when the sun is out. So our Black Matipo might be saving its attractive perfume for the evening as a extra enticement for bees to spend the night in their flower.

Unlike the iris, though, I'm presuming Black Matipo does provide a nectar reward as well. Pittosporum undulatum  is rich source of nectar for various insects and birds and I think most species of Pittosporum produce something sugary in the their flowers.

None of this I can prove having only seen the flowers in the middle of a sunny day. Do have look next time you see this hedge in flower. Perhaps pull up a chair and a beer in the evening, and see who arrives for the night.

The Black Matiop is is a tough old plant, which is why you see it, if not its flowers, a lot. It's also naturalised (that is, become self sustaining in our natural bushland) so outside gardens you see it more often than you should.

Tuesday, 3 November 2015

Signposting poisonous plants

These two shrubs growing in the Stirling Range in south-west Western Australia contain the poison 1080 (or something chemically very similar) but the sign is coincidental. They both also have leaves arising in pairs, opposite one another, along the stem. That may or may not be coincidental, but it's a useful fact.

Let's start with what 1080. Not only the year when the King of England, William I, refuses to accept Pope Gregory VII as his 'overlord', it's the product number than turned into a common shorthand for a poison we use to kill animals we don't want. The active ingredient of 1080 is sodium fluoroacetate, and in Australia it has been used to kill wild dogs, feral pigs, foxes and rabbits since, well since about when I was born in 1960.

Curiously, I think you'll agree, fluoroacetate (as potassium fluoroacetate) is also found in about 35 plant species native to Australia. These plants have often been helpfully given common names ending in Poison Bush or sometimes just simply Poison. These two are Prickly Poison, Gastrolobium spinosum, and Heart Leaf Poison, Gatrolobium bilobum, I believe,and yes, they have 'opposite leaves'.

I think all the flouroacetate containing plants are legumes. That is, they produce pods like a pea. Most are in the family Fabaceae (the pea flowered ones) but there are some poisonous wattles in the family Mimosaceae (such as Acacia georginae). All or most occur naturally in Western Australia or Northern Territory.

Another of the pea family poisonous plants is the Stirling Range Poison (Gastrolobium leakeana, also sometimes known as Nemcia leakeana), which grows a little higher up on the slopes than this sign.

So Brian (Bully) Bilney, manager and guide at the nearby Stirling Range Retreat (and featuring in the first picture), says that his friend, a local Aboriginal man, says it's easy to pick the poisonous plants in this region. If they opposite leaves, he says, don't eat them.

Simple enough, but is it true and what might it mean? I doubt every plant with opposite leaves is poisonous but then it's probably no hardship to avoid eating them anyway. As to whether there are plants without opposite leaves but also with fluoroacetate, the wattle I mentioned is at least one example. My advice, if you really want it, would be eat lettuce and broccoli mostly and to avoid any native plants unless you are with a local guide.

As to why there should be an association between opposite leaves and this chemical, I imagine that's coincidence. It is possible of course the lineage with opposite leaves evolved from plants with the poison, or vice versa. And there may be some connection chemically, an unintended consequence if you like. But this is all speculation.

Back to 1080, the poison not the year. Animals vary in their sensitivity with dogs and foxes the most susceptible. At the other end of the spectrum are reptiles and fish, which seem to be very resistant.

In between are us and native animals. Apparently it takes a lot to kill a human, but I'd avoid all plants with opposite leaves anyway - particularly their flowers and young shoots. According to my Queensland Government source, 'Australia’s native mammals, birds and reptiles have developed much higher tolerance to 1080 than introduced animals, due to their evolution with naturally occurring 1080 in some native plants'.

In fact there is much local variation in this tolerance. Western Australian bush munchers, such as the local Tammar Wallaby, are apparently partially immune to fluoroacetate while their eastern Australian cousins, not brought up in poison bush country, are not.

The emu, a seed eater, has high resistance when browsing in the south-west. The effect is less pronounced for carnivores, because they are less directly exposed to the toxin (having to eat herbivores first).

And the brushtail possum in south-western Australia is 150 times less susceptible to flouroacetate poisoning than those munching my garden plants in the east. And you can trust this research because the report comes from New Zealand, where they understand what kills possums.

So 1080 is still used to control pest animals, because it tends to kill them more than local and home fauna. As you'll see repeated repeatedly, flouroacetate also doesn't persist long in the environment, whether deposited as a bait or leaching from a native plant.

Images: from my recent trip to Western Australia, except the possum hat which is from the New Zealand Possum Marino site.

Tuesday, 27 October 2015

Asterolasia, a rare white star twinkling near a green town

It means nothing, but all three parts of the scientific name for this plant begin and end with an 'a'. Also appealing to my predilection towards gratuitous associations, the white-flowered subspecies of the otherwise yellow-flowered species grows near the green-named town of Emerald, in the Dandenong Ranges near Melbourne.

Asterolasia is a southern Australian genus in the citrus and boronia family, Rutaceae, with about 20 species. Its flowers are delicate and five-petalled; a little star-like. [Compared with otherwise similar genera like Phebalium, the outer layer of the flower - the calyx - is reduced and inconspicuous.]

Asterolasia asteriscophora is an uncommon species, found among rocks in forests from the north of New South Wales down to the Macedon Ranges in Victoria. The species name means 'starry carrier', a reference to the radiating branching of the tiny hairs all over the plant (clearly visible on the under-surface of the folded petal resting on the leaf below, and the leaf itself).

New South Wales has the one subspecies, asteriscophora, with yellow petals. Here in Victoria we have another subspecies, albiflora, a name which gives the game away: it has white flowers, or petals.

The more widespread subspecies in Victoria (and New South Wales) is called the Lemon Starbush, while the rare Emerald variant is sometimes called the Emerald Starbush here in Victoria - a little confusingly to those not familiar with the locality and expecting a flower colour hint. The name White Starbush does get official sanction in places like the Atlas of Living Australia, but do watch out for a spurious record in the west of Victoria on that site (this 1937 record from the Grampians is presumed to be incorrectly labelled).

We've been growing the Emerald Star Bush in the Cranbourne and Melbourne Gardens for a decade or so, trying to representatives of different genetic lines apart so if we need to replant at any time we have as much variety in the subspecies as possible.

Similarly in the Victorian Conservation Seedbank where we have a few different populations represented already and hope to get almost the whole range covered in time. We think the seed will last decades, maybe centuries, at minus 20 degrees, but as with all seed we need to test from time to time to make sure it remains viable.

Last time I asked (early last year) the Seedbank held 1,100 species, about a third of the Victorian native flora of c. 3,500 species. Most collections though are of uncommon species, so we have almost two-thirds of the 1,500 or so rare and threatened species in the State.

Asterolasia asteriscophora subspecies albiflora is one of those, an endangered species in Victoria, meaning it's under real threat of extinction. These days it only grows in a handful of populations near Emerald, mostly in heavily populated or semi-rural areas. In only one reserve is it found in reasonable numbers - otherwise it hangs on, often insecurely, in roadside remnants or on private property (thankfully a few 'convenanted' properties are established, or about to be established, near to Monbulk).

While seedlings germinate after some fires (they benefit from smoke stimulation), they appear to need at least a five-year gap between burns. In addition to ill-timed fires, loss and degradation of habitat puts pressure on these remaining populations, as do invasive native and exotic species.

The Emerald Starbush was given a scientific name, Eriostemon spathulifolius, back 1913 but omitted from subsequent floras as a minor flower-colour variant of Asterolasia asteriscophora. Following a detailed study of this species across its entire range (published in Muelleria, volume 16; 2002), Brian Mole recognised the Emerald populations as distinct but at subspecies level. It not only has distinctive white petals but various other attributes such as generally smaller leaves and flowers, and somewhat differently shaped leaves.

So even apart from its tautogramic (and matching posterior-tautogramic) scientific name - Asterolasia asteriscophora subspecies albiflora - the Emerald or White Starbush is a plant worth looking after.

Images: All taken from a single potted plant in the Melbourne Gardens nursery, on 12 October 2015, just past its flowering peak. Thanks to Neville Walsh for much of the information and some editorial checking, and to Rob Dabal, Conservation Officer with the Port Phillip and Westernport District for the latest on conservation efforts near Monbulk.

Tuesday, 20 October 2015

Whimsical cartoonist plants wonky desert cypress

Yesterday, cartoonist and poet Michael Leunig planted a tree in our Melbourne Gardens. At first we sought a curly plant of some kind, such as one of the 'tortured' willows or hazels, but we settled in the end on a tree with just a hint of asymmetry and one that should survive Melbourne's toughening climate - the Saharan Cypress, Cupressus depreziana.

This is the second in our rebooted Commemorative Tree program, following at a safe distance behind musician Nick Cave's planting of a Henry's Lime in December last year. Michael Leunig is of course a much-loved social commentator in Melbourne and someone willing to speak his mind and hold strong opinions.

The selection of Leunig was consistent with the choice of Nick Cave, both having with a distinctive individual style and representative of creative and liberal Melbourne. His contributions to Melbourne and the world's cultural life have been over an extensive period, and a little 'outside the box'. For 46 years he has been contributing his whimsy and wit to newspapers, and in July this year he celebrated his 70th birthday. As a bonus, Leunig regularly references trees and nature in his pictures and writing.

So to the tree itself. Not really curly but it does develop a curious habit. The Saharan Cypress is, as you'd expect, a rather drought tolerant conifer. It's from the central Sahara Desert, growing above 1000 metres in the Tassili n'Ajjer Mountains, in eastern Algeria. It was brought to the attention of western scientists by Captain Duprez, commander of a French army camp stationed nearby.

There are only 233 individual plants remaining in its native habitat. So few, and they are so long-lived (the oldest dated at 2,300 years old), that each tree has its own name. These names in the local Tamashek language relate to location (the one near the flat stones, or a mountain), use (to hand things on) or perhaps an important nearby feature (pool of water at its roots).

Tamashek also provides an intriguing common name, Tarout. 'Tarout' is a butcher's term for the windpipe and attached lungs of an animal, and due to its wonky top our tree will eventually have a passing resemblance to this collection of internal organs (held windpipe-down...). Not curly, but a little off-centre perhaps. Perhaps also a nod to Leunig being the son of a slaughterman and having worked in abattoirs in his early years...

The Saharan Cypress is more common in cultivation, particularly it seems in Australia where a thicket of the Saharan Cypress and its close relative the Moroccan Cypress (sometimes considered to be a variety of Cupressus depreziana, called var. atlantica) were planted eight years ago in the National Arboretum in Canberra.

In the Algeria mountains summer maxima are around 20-30 degrees C, and winter days 1-13 degrees C. Not unlike Melbourne, although we get a little hotter in summer. Annual rainfall is variable but around an extremely low 30 mm, compared to our current 650 mm a year in Melbourne.

While we anticipate a more extreme climate in Melbourne over coming decades we don't expect rainfall to drop that much. On the other hand we are always on the look out for plants that need less water and are able to survive the occasional drought. We expect this species will do just fine in Melbourne Gardens.

And if it does, we can tell the story not only of its exotic origins and endangered status, but also of its male dominated reproduction. At least some of the time the Saharan Cypress employs what is called apomixis, where seeds develop without sexual fusion. In this particular case the important genes all come from the pollen, the male 'parent'. It seems the female 'parent' provides nutritional content for the seed but none of the genetic content that ends up in the new plant.

It's unclear if this happens all the time, or why it happens. It may be that in the small remnant population in Algiers there are no longer any viable female reproductive cells produced. Odd things can happen when you get a small number of individuals interbreeding.

The specimen Michael Leunig planted yesterday, 19 October 2015, has been doing very nicely in our nursery (modeled here next to Dermot Molloy). Its success out in the Gardens will depend on how its genes, whatever their origin, allow it to respond to our ever changing Melbourne climate.

Tuesday, 13 October 2015

Albany's pitcher plant like no other

In near coastal swamps from Albany west to the Indian Ocean, you might find one of Australia's four species of pitcher plant. In August this year I didn't, despite being given some pretty precise instructions by local botanist Professor Steve Hopper. Instead I spent a pleasant hour or two photographing a few of the other species that frequent this coastal wetland, such as Bridal Rainbow (Drosera macrantha, a sundew), Southern Cross (Xanthosia rotundifolia in the carrot family) and the Albany Daisy (Actinodium ?cunninghamii, in the myrtle family rather than a true daisy).

The pitcher plant familiar to most of us is the Nepenthes, usually a scrambling or climbing tropical plant with 'pitchers' formed at the end of a tendril extending beyond a typical looking leaf. Three species occur in the far north-east tip of Australia (Cape York), an extension southwards of a genus mostly found in South-east Asia.

The trumpet pitchers, Sarracenia and its relatives in North America and the top of South America, convert an entire leaf into a pitcher. They grow on the ground, mostly looking like elegant tall vases, or trumpets.

The third kind is Cephalotus, with inner leaves typical and outer leaves adapted into pitchers. It only grows in the far south-west corner of Australia, in those aforementioned swamps. According to Steve Hopper and Paul GioiaCaphalotus is a 'highly divergent relict of a rainforest lineage'. 

These three different kinds of pitcher plants are not at all closely related, each responding independently to poor boggy soil by producing an insect catching and digesting trap to extract nutrients from hapless visitors. A few other plants, such as bromeliads, are thought to deliberately catch insects in a similar way, and there are 580 or so species in 20 genera and 12 different plant families that have a carnivorous life style of some kind.

Cephalotus means 'with a head' referring either to the lid on the pitcher or more likely the swellings on the male-bearing structures above (the stamens with their yellow anthers); it's an evocative name, as evidenced by it being taken up by a death metal band from Tokyo. There is only one species, Cephalotus follicularis, with the species name meaning 'little sacks', a certain reference to the pitchers.

The Albany Pitcher Plant was probably first seen by botanists in 1791, when collected by Archibald Menzies. The species wasn't formally described and named until 15 years later, after French biologist Jacques-Julien Houtou de Labillardière examined material brought back to Europe (via Java and England) collected by Jean Baptiste Leschenault de la Tour on the expedition to Australia led by Nicolas Boudin. Although I do note David Mabberley, in his The Plant-Book, says it was discovered by Robert Brown in 1801.

As with the the other plants mentioned here, the pitcher acts as a 'pitfall trap' for insects and other small prey (the Cephalotus traps are at most 6 cm across). Nectar is the attractant and the slippery upper ridge with downward pointing teeth means once inside the insect struggles to escape (the lid is more to keep rainfall from diluting the digestive soup inside than to stop anything getting out).

It's odd that we should have two quite different kinds of pitcher plants at two extreme ends of Australia, almost as far from each other as possible. But then it's a odd country with an often odd flora and fauna. The odd things often tell us a little about our country's cultural and natural history.

Images: Images of the Albany Pitcher Plant are by Barry Rice, from the International Carnivorous Plant Society pages. The other images are from hour or two wandering around likely habitat.

Tuesday, 6 October 2015

Cultivating the gopher spurge, for climate change

I've written about euphorbias that look like cacti, and some that don't. I've also mentioned before that if a flower looks odd and you can't work out what family it's in, then it's probably a member of the Euphorbiaceae. You could add that if the flower is nothing to write home about, ditto.

This one in Castlemaine's Botanical Gardens is a common bedding plant, Euphorbia rigida. It will be part of adapting the botanic garden's plant collection and landscape to a drying climate, something that no doubt would have been useful right from the inception of the garden more than 150 years ago.

Still, things are likely to get tougher for plants in south-eastern Australia as we blaze our way into the twenty-first century. At Melbourne Gardens, we have included this species in our low-water-use garden. This next picture is from that garden, the rest in the post from Castlemaine.

At Castlemaine in July, the plants were starting to flower. Early days but things don't get any more colourful or particularly dramatic as flowering progresses. Inside each of the leafy cups is a group of very simple flowers, a few male and one female, and without any further adornment such as petals. This rather odd arrangement of reduced flowers is called a cyathium and it is common in the family Euphorbiaceae.

Perhaps more interestingly, this species, like all euphorbs, contains a white milky substance. You may remember Euphorbia peplus, the source of a cure for skin cancer. Often the exudate is both poisonous and irritating to the skin, but it also has become another potential source of biofuel.

Euophorbia rigida is one of the species commonly reported in biofuel trials. It's popular in places like Turkey because it is widespread and, as we know, able to grow with little water or attention. The Gopher Spurge, as it is sometimes called, grows naturally around the Mediterranean and through the Middle East.

So this plant is an interesting mix of a good garden substitute for drier times and a possible source of energy to replace damaging fossil fuels. The perfect climate change plant? You just know the down side is that it will be weedy. Well, not in Victoria, at least yet. There are only two records in Australia's Virtual Herbarium, both from the Swanston Street Mall in central Melbourne collected 20 years ago, and none in the Atlas of Living Australia.

I notice there are reports of Euphorbia rigida escaping into native vegetation in California, but at least in 2012 it was not considered naturalised - i.e. persisting and reproducing in nature. Do keep an eye on it and definitely don't dump it into bushland (which should go without saying of course) and for now, enjoy.

Tuesday, 29 September 2015

Dancing bones in a drunkard's dream

This is a cactus, but an unusual one. You may be familiar with the Easter Cactus (Hatiora gaertneri) or Christmas Cactus (Schlumbergia) with their flattened stems and relatively large red flowers. Like that species, Dancing Bones grows on trees or rocks in the tropical rainforests of south-eastern Brazil.

In a tree, or on a rock, the plant finds itself separated from the more reliable water supply that most plants source through their roots, so being a succulent (with fleshy, water-storing stems) is as much of an advantage as it is out in the desert. Dancing Bones grows quite happily in a normal potting mix and, in this case, on an inside windowsill facing south.

With its distinctively shaped segments, you can see why it might be called Dancing Bones. Its other common name, Drunkard's Dream, is a reference to the plant sometimes looking like a string of bottles. The segments range from sausage to almost baseball club shaped.

Its botanical name is Hatiora salicornioides, although you sometimes see it referred to as Rhipsalis salicornioides (it has taken some time for the classification of these 'epiphytic' cacti to be resolved). The species epithet, salicornioides, refers to its resemblance to the common salt marsh plant, Salicornia (a chenopod).

Dancing Bones was introduced into cultivation in England in 1817, and made it out to the colonies by 1850 (it appears in the 1850 and 1857 catalogues from Camden Park in New South Wales).

These days there are five species of Hatiora, including the Easter Cactus. That species flowers in early spring in the Northern Hemisphere - around March or April - hence its name. Dancing Bones seems to have a similar flowering cycle, although perhaps starting a little earlier, with its flowers opening in August (i.e. February in the North; and in Europe I've seen reports of it flowering in January as well). Drying out may also stimulate flowering: in my case I water it once a week, but hold back a little in winter.

Unlike other epiphytic cacti, the Hatiora have stem-segments mostly different from one end to the other (hence the bottle and bone terminology) as well as flowers at the end of the branches. Some of the segments on branches drooping below pot level have lots of fine 'needles', but hardly the spines of our desert cactus and not as irritating (it seems) as the glochids of an opuntia.

The flowers are small, about five millimetres long, and they look like...well, this. They open and shut each day, for a few days, although never seeming to fully open on my windowsill. Pretty enough close up, but not a show stopper.

The berries that follow are not much showier, being translucent with a reddish tip (leading to another common name, the Mistletoe Cactus). Sadly my plant didn't produce any fruit: the final flower, and possibility, dropping last week. Still, it is a curious plant, and it has some funny names. 

Images: All from this plant growing on my work windowsill.

Tuesday, 22 September 2015

Magnolia reveals leafy road map

For much of the twentieth century there were a dozen genera in the family Magnoliaceae, with the namesake Magnolia the best known. You may also have heard of Michelia (including the Port Wine Magnolia) and Liriodendron  (the two Tulip Trees).

As the Magnolia Society International explain, the number of genera was reduced back to seven in the 1980s although, apart from the Tulip Trees which everyone accepts as distinct, this system was not accepted universally. Not to worry though, the advent of DNA sequencing led to an even better understanding of the family and evidence that all the smaller genera apart from the Tulip Trees were embedded within the family tree of Magnolia. Now there are two genera only, one with 13 sections (there could have been 13 genera but the genetic differences were small, the identification of some groups difficult and it would have resulted in even more disruption to names).

The flowers of Magnolia no matter how you circumscribe it, are what you first notice. Big, bold and full of stamens (male bits) wrapped around a cluster of carpels. This used to be considered a 'primitive' flower structure but that mantle is now bestowed on the rather simpler flowers of plants like Amborella (although the whole concept of a flower today being primitive is not very meaningful).

It wasn't the pillowy white flowers of this species of Magnolia that grabbed my attention this time but something more subtle, something I only noticed when I was photographing the leaf to help me identify the species, Magnolia doltsopa (once Michelia doltsopa) I believe.

I noticed first the leathery upper surface, but then the intricate patterning of the veins. This is what we call reticulate, or networked, venation. Like a net.

In this case, and it's not always the case, he final threads are 'free' - not connected to anything. So instead of it being a web, there are dangly bits inside each of the smallest defined areas (called areoles or areola). It's like an irrigation system, getting the drips or sprinklers evenly spread so the water can reach as much of the area as possible.

In a way this is what the veins do too. They are more technically called vascular bundles, and they do act as a kind of vascular system similar to the one that carries blood through our own bodies. Instead of blood the bundles carry water (and nutrients) from the roots to the leaves where it is needed as part that vital chemical reaction photosynthesis, and then the energy-rich products of that process, sugars, to where they are most needed in the plant. There are two sets of 'pipes', the xylem carrying the water and the phloem carrying the sugars.

What you see in a leaf are the outlines of this transport system. The main veins are the first thing you notice. They are usually parallel in what we call often call Monocots or Monocotyledons - grasses, lilies and the like - and more often spreading out from a main central vein in the Dicots with their mostly broad leaves. There are lots of variations and in fact it can be a useful identification character.

In this species the patterning is the same on the top and bottom, with just a different sheen. The top is brown and leathery, the underneath whitish with a tint of blue.

To identify this particular Magnolia (as a Michelia as it happens) in the Horticultural Flora of South-Eastern Australia (Volume 2) by Roger Spencer, I had to count the main veins and confirm there were less than 12. I didn't have to look to any of the finer detail in this case but sometimes that's important too.

Putting aside its value to the plant and to taxonomists (those who name and identify plants), the venation is just a fascinating construct. Clearly it's a good way to maximise the reach of your plumbing and transport system, as any property developer knows...

Update 27 September 2015: See latest from Royal Botanic Gardens Kew on new chemicals discovered in Magnolia.