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.

Tuesday, 15 September 2015

The double-r, double-n, double-flowered Sparrmannia

We have quite a few of these double-flowered cultivars of Sparrmannia africana in the Royal Botanic Gardens Victoria. 'Flore Pleno', as it's called, suckers readily and tends to form clumps 3-4 metres high and across. The single-flowered form is, to my mind, far prettier but all of ours in flower at the moment are doing this fluffy thing.

In our database the species is listed as a member of the lime tree family, Tiliaceae, consistent with some of its Common names in Europe: German Linden, House Lime or Indoor Linden (although the latter name is sometimes applied to another species, Sparrmannia ricinocarpa). More recently this family has been combined with others into an expanded mallow family, Malvaceae.

The leaf looks a bit like a Tilia (lime or linden), the soft stems make you think of a Hibiscus (mallow) and the hairiness is a bit like a Brachychiton (in the Sterculiaceae, now also part of the Malvaceae). So I'm not too fussed either way.

As the species name and another common name African Hemp suggest, this perky shrub is from Africa. It is also know as Cape Stock Rose and Cape Hollyhock in honour of its natural habitat, in damp forest margins and hillsides around the Cape of Good Hope. The whole genus in fact is only found in Africa and Madagascar, and contains between three and seven species (its taxonomy and nomenclature seems a little uncertain).

Alice Notten, from Kirstenbosch National Botanical Garden in Cape Town, provides some excellent background to this species and its nomenclature on the South African National Biodiversity Institute’s PlantZAfrica site. In the single-flowers (prettier) form the flowers have a brush of red and yellow stamens (male parts with pollen) protruding from the white petals. As Notten says 'much of the attraction of this flower is in the puff of brightly bicoloured stamens'.

These stamens are sensitive to touch and 'puff out' when a visiting insect bumps against them, spraying it with pollen. But it gets better. Another way the plant encourages insect visits, and therefore potential pollination, is to offer up sacrificial stamens, with knobs, to be eaten.You can see them in this gorgeous image taken by Stewart R. Hinsley and reproduced from the Malvaceae pages.

You sometimes see the name Sparrmannia spelt with one less 'r'. This is because in the original description, by the son of Carl Linnaeus ('Carl Linnaeus the younger' or 'L.f.'), the name was rendered incorrectly. It took over two centuries for this to be fixed but he name has now been 'conserved' with the correct spelling as this was clearly little Carl's intention (he actually spelt it correctly when he got to listing the species). 

Anders Sparrmann was a Swedish surgeon and botanist, travelling with James Cook on his second world voyage and then later collecting around the Cape. He introduced Sparrmannia africana into cultivation in Europe in the late eighteenth century, where it became a popular glasshouse plant (the Indoor Linden...).

That cover most of the names you'll see used for this species. As to African Hemp, fibre has been extracted from this plant but of low quality. And flore pleno is Latin for 'full flower' and is used in horticulture for double-flowered forms (although I wonder if this particular cultivar has more than one extra later of petals - I'm assuming that every stamen has been replaced by a petal, as we saw in the hellebores.

Plenty of flower, and flowers, to enjoy and plenty of time to do it. In South Africa it can bloom from mid-winter to early summer. My pictures were taken at the start of the flowering season, in early July (with all plants yellowing a little), and it is still floriferous now.

Tuesday, 8 September 2015

From little things big green walls grow

I've questioned the value of 'green walls' at times (e.g. Blueprint for Living, Talking Plants on RN), but I've also made a few complementary remarks from time to time. In this post I want to focus on one building, One Central Park in Sydney, with its 150-metre-high vertical gardens designed by green-haired Patrick Blanc.

These green walls were promoted as the tallest in the world when installed a few years ago. The largest living wall in Europe was claimed by a power company in the UK, when it wrapped its car park in planters. A 7-storey green clad building destined for Brisbane will support a 489 square metre vertical garden that, it says, rival some of the biggest in the world.

All fine I guess but the cost of installing and maintaining these walls has been weighted up against their environmental and social benefits. Apart from the engineering needed to keep the plants where they are, there is the huge water budget needed unless you plant particularly wisely.

Anyway, we can judge them all over time. This is what that art installation on One Central Park looks like today (or at least in June when I took these pictures) about two years after its actual installation.

Yet...,the building itself looks pretty good still. It looks green and it looks like a greenish wall thanks not so much to the massive vertical gardens but to the plantings on the apartment terraces. I'm presuming the terrace gardens are part of fellow Parisian architect Jean Nouvell's concept and brief, although no doubt with some assistance from Mr Blanc.

The well proven way to green a wall is to plant something like Virginia (Parthenocissus quinquefolia) or Boston Ivy (Parthenocissus tricuspidata) against the wall, or 'espalier' (training/pruning a plant to grow flat against a wall) something. The Botany Building at the University of Melbourne has just planted a clutch of ginkgo which they are planning to espalier against the wall of the building facing their Systems Garden. On the front wall they already have Boston Ivy doing a fine job.

But this post is all about One Central Park, so here are a few more pictures that show off the successfully green bits of this striking and likable building, which to be fair includes some of the Blanc walls along with those botanical balconies.

Note: Landscape Architecture Magazine features the building and its garden in its July 2015 issue, with Carol Becker providing much more insight into the engineering and design behind the project. 

Tuesday, 1 September 2015

Diverse Stirling Range orchids right on the money

On average, if you wander around identifying plant species, one in every dozen will be an orchid. Many species will be more common than orchids and in some regions of the world you might not find a single orchid, at least out of season, but we share this planet with a remarkable variety of orchids. This is just one of the Australian sun orchids, called Queen of Sheba.

Of Australia's 800 or so species, more than 120 grow naturally in the Stirling Ranges in south-western Western Australia, where I spent a few days looking for freshwater red algae (my research obsession) and checking out attractive flowers on the way. In that mountain range, the percentage of orchids is bang on 8% of the flora, as it is worldwide (a whopping 25,000 of the plant species alive today - 300,000 - are in the family Orchidaceae, the biggest plant family by far).

These next pictures are of spider orchids, specially adapted to attract.copulating male wasps as pollinators.

On a fresh August morning, Brian ('Bully') Bilding from Stirling Range Retreat, showed me around 25 species of orchid in just over three hours. Not bad for a group of plants that flower seasonally and spend most of their time reduced to a tuber below the ground. I'd scratched around the afternoon before, finding half a dozen of these. It definitely helps to know your neighbourhood.

To be fair Western Australia is the place to go if you want to see a large chunk of most of this country's floral diversity. While I was there in August the Western Australian Herbarium added the 10,000th published addition to the State's native plant census (FloraBase). There are many more to be described with the total flora currently estimated at 12,437 - that includes known species yet to be described but not plants assumed to be out there but yet to be discovered.

If you look at the total flora of Australia, with around 25,000 species, Western Australia has about half and most of these are in the south-west. To look at it another way, the native flora of the Stirling Range (1,200 square kilometres; 1,500 species) has more plant diversity than the entire United Kingdom (244,000 square kilometres; 1,400 species - although some might quibble about adding migrants since the sixteenth century).

These last three are greenhood orchids, with triggering mechanisms that dump sticky clumps of pollen onto visiting insects.

In total Western Australia boasts about 430 orchid species, compared to the 350 or so in Victoria, the next richest State I would suspect. Lest you protest about the size of WA, I reckon the vast majority of the species grow in the south-west corner, an area smaller than Victoria. And another 17 species of spider orchid (more or less in the genus Caladenia) were freshly described from the South-West this year!

A recent phylogeny (the tree of life, showing how each species is connected to its closest relative with a shared ancestor) of the Orchidaceae showed that the evolution of a 'pollinia' - those sticky clumps of pollen - evolved at least 64 million years into their 112 year old history as group distinct from other plants. Those lineages with pollinia diversified quicker than those without - intricate one-on-one battles with insects loomed, such as the one I described in the Star of Bethlehem Orchid from Madagascar.

Another major step, by 35 million years ago, was heading up into the trees. Like bromeliads, succulents and various other plants surviving in dry habitats, orchids also developed a special form of photosynthesis (using energy from sunlight to convert water and carbon dioxide into oxygen and sugars) called Crassulacean Acid Metabalism (or CAM for short; I will blog about it, one day...).

A final step towards 'world domination' was heading up into the mountains, sometimes in trees, sometimes not. (As yet the production of insect-attracting scents - pheromones - cannot be implicated in diversification - but scientists expect there has to be a sniff of this somewhere in the phylogenetic tree.)

As if to confound all this, about three-quarters of all Australian orchids are ground or terrestrial orchids and the vast majority live in the lowlands or mildly hilly country. Perhaps as with much else in the Australian flora simply isolation and time has resulted in plenty of charming species to photograph. Such as this Blue Beard which, unlike all the other species, also occurs in Victoria.

Images are all orchids from the Stirling Range, photographed on 24 August 2015 (it was hard to leave any out but the out-of-focus-due-to-wind images excluded themselves.) My stab at their names, being a foreigner to these parts, is, from top of post: Thelymitra variegata (Southern Queen of Sheba), Caladenia plicata (Crab-lip Spider Orchid), Caladenia longicaudata (White Spider Orchid), Caladenia flava (Cowslip Orchid), Pterostylis recurva (Jug Orchid), Pterostylis barbata (Bird Orchid), Pterostylis concava (Cupped Banded Greenhood) and Pheladenia (previously Caladenia then Cyanicula) deformis (Blue Beard).

Tuesday, 25 August 2015

Beaked buds by a billabong

Back in the early years in this blog (November 2009) I wrote about the River Red Gum being split into seven subspecies, river red gumlets I christened them. In that post I talked about how the species name, camaldulensis, comes from the name of a garden in Italy.

That garden was L'Hortus Camaldulensis di Napoli and its head gardener and German botanist, Friedrich Dehnhardt. In 1832, Dehnhardt described and named the River Red Gum Eucalyptus camaldulensis from plants growing in this private botanic garden just out of Naples.

For a hundred years though the name Eucalyptus rostrata was used for River Red Gum, at least in Australia. We can thank another German botanist Diederich Franz Leonhard von Schlechtendal for this name, which he published in 1847. What we can't think him for is is lack of scholarship. Not only did Schlechtendal miss the fact that the River Red Gum already had a name, but he also overlooked the fact that species name he chose to bestow upon it was already taken, by the Swamp Mahogany.

Fifty years earlier, in 1797, the Spanish botanist Antonio José Cavanilles had named the Swamp Mahogany Eucalyptus rostrata. Sadly that application of the name rostata has also been relegated to what we call a synonym, with the Swamp Mahogany being named Eucalyptus robusta two years earlier, in 1795, by the English botanist James Edward Smith.

Generally in plant plant nomenclature, the earliest described name is the correct one: for Swamp Mahogany, Eucalyptus robusta and for River Red Gum, Eucalyptus camaldulensis. While we might gain a quaint historical vignette through using the Italian name we lose a little in the identification stakes.

'Rostrum' is Latin for beak, and compared to most other species of eucalypt, the 5-10 clustered flower buds of the River Red Gum are 'beaked'. Other buds are longer and narrower (many are like clown hats) and some are short and nipple-like (which is how I would describe those of the Swamp Mahogany as it happens, so the name rostrata would have been wasted there!). Few would be confused with the pointy-beaked buds of Eucalyptus rostrata... whoops, Eucalyptus camaldulensis.

The cap - whether extended, beaked, nippled or simply domed - replaces the petals (and in this case the layer outside the petals, called the sepals, as well), and is the source of the genus name 'eucalyptus', meaning well covered, a reference to way this 'operculum' protects the flower until it is shed revealing a brush of stamens (the male parts of the flower bearing pollen).

The other distinguishing feature of the River Red Gum is the way the disc around the top half of the fruit (the gum nut) curves upwards and inwards. Eucalypt fruits also express themselves in a range shapes, sizes and analogues.

One of most cherished books as a young botanical student was Eucalyptus Buds and Fruits: Illustrations of the buds and fruits of the genus with a list of authentic specimens from which the drawings were made, edited by George Chippendale. Yes a very nerdy book for a nerdy 18 year-old just becoming immersed in the plant world after dumping physics and maths in first year university. I went straight to it the other day when I discovered these and other fruits and buds beside the Yarra River in Hawthorn.

But if you don't want to look this closely the other diagnostic characteristic of the River Red Gum is where it grows and how common it is. If you see a gum-barked (apart from the base) tree growing next to a river, creek or billabong in mainland Australia, it's most likely this species. Or less commonly a Swamp Gum, Manna Gum or maybe Candlebark... but their buds don't have beaks.

The last thing that singles out a River Red Gum, often, is its ability to survive and to wear its scars. It is not always a classically beautiful tree but it can be a resilient one. Which is a certain kind of beauty in itself.

Images: Except the last (which a remnant in the town of Buninyong, near Ballarat, photographed in June 2015) the pictures are of a few relatively young trees planted beside the Yarra River, taken in July 2015.

Tuesday, 18 August 2015

Humboldt's single bristle gives bees a leg up

There are more than 50 species of Monochaetum, all of them from the mountains of Mexico and down through to the Andes. This one is Monochaetum humboldtianum, named after Prussian explorer and naturalist, Alexander von Humboldt, whose most famous journey was to Central America in the first years of the nineteenth century. The species grows naturally in the Coastal Range of northern Venezuela.

You'll notice that the leaves and flowers look a lot like Tibouchina, a common blue and sometimes pink flowered tree in Australian gardens (particularly the popular cultivar 'Alstonville', of Tibouchina lepidota, which was bred at Alstonville in northern New South Wales). Tibouchina has a similar distribution through Central and northern South America.

Look again and you might notice there are four petals on this flower (which is more pink than purple in nature) I photographed in our Melbourne Gardens. That's different to Tibouchina, which has five.

Deeper inside the flower it again looks superficially similar to Tibouchina, with two kinds of stamens (the structures that bare pollen in the flower), but in Monochaetum the group of stamens opposite the petals are larger than those opposite the sepals - the reverse is true for Tibouchina. Each of the stamens, big or small, has two arms, one technically an 'appendage'.

In the case of the stamens arising opposite the petals, the appendage looks just like the pollen-bearing (anther). This makes it look like a forked anther of some kind - you can see this in the bottom right of the following picture. The other stamens, the ones opposite the petals, have a long purple appendage reflexed downwards and reaching out to the style.

All this is quite different to the flowers of Tibouchina (which we used to sometimes call Lasiandra), illustrated here from Wikimedia Commons:

There are other genera in the family Melostomataceae with four petals and they don't look wildly different. In fact this particular specimen near the Green Waste Recycling Centre in the Melbourne Gardens isn't on our 'living plant census'. The closest you'll find, in location and taxonomy, is Centradenia grandifolia which is purportedly in a garden bed just around the corner. In fact what I found there seems to be a different genus again, with five petals.

But for arguments sake let's assume there are some Centradenia in the Gardens somewhere. That genus has leaves that are asymmetrical at the base, and different in size overall compared to the leaf opposite it on the stem (i.e. anisophylly; although the smaller leaf is sometimes deciduous when young, making it sometimes look like the leaves are what we call alternate rather than opposite). The stems are also 'winged', with four angular ridges. All unlike our vegetative plant, which looks like this.

I'm happy my plant belongs to Monochaetum humboldtianum. It gives me the chance to mention Alexander von Humboldt, as I've done, and to point out that 'monochaetum' is Greek for 'single bristle', a reference to the purple appendage I mentioned above. Most genera in the family Melostomataceae have this appendage, but this one is named after them! Because they are pollinated by bees, using buzz pollination, it's thought the appendages held the bees get a foot hold.

Charles Darwin was fascinated by the stamens in this family and in addition to growing and crossing plants himself, he sought detailed advice from botanists such as George Bentham. This quote is just the start of a letter that continues with torrent of detailed questions about their floral architecture, bulling Bentham into examining herbarium material on his behalf.

We have a few other shrubby species of Melastomataceae in the Melbourne Gardens collection, including Melastoma malabrathicum from Asia but now a weed in North America. The family name, Melastomataceae, comes from Greek words meaning 'black mouth', and according to Royal Botanic Gardens Kew's Neotropical Melastomataceae page that is what you will get if you eat the purple or blue berries. In June when I took these photographs, Monochaetum humboldtianum was clearly flowering, which was a nice winter treat.