Tuesday, 24 March 2015

Sexy persimmon

A few years ago Jane Edmudson on the ABC’s Gardening Australia described some persimmons as suitable for eating like an apple. Others, she said, are almost inedible due to their astringency. There are some 1000 cultivars so you have plenty to choose from.

As you’d expect if you read my recent post about how the Globe Artichoke can change our sensation of sweetness, it’s the phenolics in persimmons that pucker your mouth. In this case, mostly tannins.

Apart from causing mouth puckering, the tannins in the fruit of Diospyros kaki, the persimmon, can be used for waterproofing, food preservation and dyeing. The fruit and leaves also have some potential medicinal uses, currently under investigation: I gather you might already find persimmon extract in 'athlete's foot socks and soap'.

As I discovered in my local park, where a single persimmon tree has been placed among a collection of other edible-fruit trees, the flowers are either male or female. Although on the same plant in this specimen, they can sometimes male on one plant and female on another.

The females (above) have the green, leathery, almost-Elizabethan collar that ends up ornamenting the fruit (see top of post). The male flowers (below) are pretty insignificant in comparison, and look like they might just be spent blooms.

Varieties that produce fruit without seed don’t need to be pollinated, but fully loaded fruits need male flowers in the vicinity. In US orchards farmers grow trees in a ratio of eight female to one male, although I did read that trees can change their sexual orientation from year to year, which if true would make this tricky!

So I tracked down some authoritative advice from the University of California in Davis (USA) on, as they put it, 'what makes a persimmon a boy or a girl'...

One in 20 plant species have flowers on a single sex. It's a great way to mix up genes during pollination, making sure flowers don't pollinate themselves or, if the flowers are on separate plants, don't pollinate with flowers on the same plant. There are other ways to stop this happening, but dioecy, as it's called when single-sexed flowers are on separate plants, is a good way.

The scientists at University of California say persimon plants are either male or female, which makes my parkland plant a little odd. My plant would be described as monoecious meaning that while it has single-sex flowers (either male or female) these are born on the same plant. A dioecious plants has only male, or only female, flowers.

This I remember from Botany 101, or whatever we called it, although the terminology gets a little confusing when transferred to algae, where I drifted later in my studies...

So this, my parkland plant, is monoecious and my American university colleagues say persimons are dioecious? I needed to read more closely... These guys were working on a different species of persimmon, Diospyros lotus, sometimes called the Date Persimmon or Lilac Persimmon. It has smaller fruits and, it seems, a slightly different sex life.

The researchers were looking for the gene that coded for maleness or femaleness. That is, what makes it a boy or a girl persimmon? They found a gene system they call OGI-MeGI: ogi is Japanese for male tree, megi for a female tree. Their next task is to see if this kind of system is universal in all plants, and to see if they can introduce dioecy into the 95% of plants that don't have unisexual flowers on separate plants to help with breeding and plant health.

Meanwhile, back in the park, I'm going to have to track this plant to see if it keeps producing flowers of both sex (monoecious) or switches to only one sex (dioecious). I'll get back to you in a few years, perhaps.

Images: The flowers and young tree are from the park near where I live, photographed in December 2014, and the fruit from a Grow Organic website.

Tuesday, 17 March 2015

Puka might go to pot

This is the Puka, or Meryta sinclairii, a species growing naturally only on Three Kings islands off the far north of the North Island of New Zealand. These islands are at a latitude of 34 degrees south, pretty much the same as Sydney.

A New Zealand species with subtropical attitude, it is dotted all over Melbourne's Royal Botanic Gardens. And as you'd expect from something in the ivy family (Araliaceae), it's not about the flowers. Nineteenth century Director William Guilfoyle knew this. The Puka was part of his plan to contrast leaves of varying shape, size, texture and colour.

As pointed out in the booklet A Gallery of Plants (1992) by Ros Semler, this species is a distinctive element in the garden beds around the Nymphaea Lily Lake, all of which continue to display Guilfoyle's design intent in regard to diverse foilage. Meryta sinclairii rates a mention in most books on Melbourne's Royal Botanic Gardens.

The leaves are chunky and at first blush a little like those of some mangroves, such as Clusia. In its native habitat it grows mostly in sheltered, moist valleys but it seems to do well out in the open and with minimal watering, albeit with a little leaf burn off in the Melbourne summer (this next picture, and others from the Royal Botanic Gardens, were taken in mid-January).

Our plants flower, although I don't know how regularly. There are separate male and female flowers, both nondescript, with the female flowers followed by ivy-like berries. I found some flower buds (in January) on a bush on the Ornamental Lake side of what we call the Central Lawn, but only a few remaining fruit. Here is a picture of those precient buds, followed by an picture of young fruit on a specimen growing in New Zealand, photographed by Warren Brewer (©)

According to the online Flora of New Zealand, Puka was first collected for science from a single plant growing at Paparaumu, in the Whangaruru Harbour, about 150 km north of Auckland. The soon to become Director of Kew Gardens in London, Sir Joseph Hooker, described it as a new species in 1852, in a genus called Botryodendrum. That genus has since been split and subsumed, with most species relegated to Meryta which now has about 28 species.

The Wikipedia entry has a ring of authenticity about it so I'll chance repeating this tale. William Colenso, the first European to find the specimen at Whangururu Bay was frustrated in his attempts to collect flowers and fruits - he visited regularly over a number of years but found none. Both he and the Colonial Secretary Andrew Sinclair sent leafy stems to Sir Joseph who eventually got fertile material, off the same tree, from a William Mair.

From the same source I can report that the Puka has the largest entire (that is, not divided into smaller leaflets) of any New Zealand plant. Sounds about right, and supported by a comment reiterated by Ross Beever in his paper on the natural distribution of the species, that the Puka is the only 'true macrophyll' in the New Zealand flora.

Most of the 28 species of Meryta are found in the tropics and subtropics, with a whopping 11 found in, and only in, New Caledonia (a lot, but two fewer than there are Araucaria species there...). There are no species native to mainland Australia or mainland New Zealand - just the one species, the Puka, on the Three Kings Islands (and introduced onto the nearby Hen and Chicken Islands) and two (Meryta angustifolia, Meryta latifolia) on the more-or-less-self-governed Australian territory of Norfolk Island.

Meryta sinclairii is uncommon and at risk of extinction in its natural habitat. The New Zealand Plant Conservation Network - an at all times thoroughly reliable source of information - note that the remnant natural populations are under threat from marijuana growers who like using remote islands to grow their crops. It's not that the ganja outcompetes the puka, but the illegal farmers often bring with them deadly (to the Puka) fungal pathogens.

Tuesday, 10 March 2015

Titan Arum's honorary flower

When the Titan Arum blooms - as it does regularly in glasshouses all over the world these days - botanic gardens' spokesfolk, such as me, employ all kinds of linguistic contortions to describe the structure of the 'flower'. This gigantic thing is a collection of tiny male and female flowers, with some fancy trimmings.

As most people now know, when the swollen green 'flower-bud' opens, a purple pleated skirt is unfurled, exposing the lower half of a yellow banana-shaped object that seems to have the texture of chamois leather. A powerful and rank smell rises from deep within the now skirted banana, attracting in its native land of Sumatera various flies and beetles. In botanic garden glasshouses, the descriptively named Amorphophallus titanum attracts people, as you can see here in Sydney Royal Botanic Garden's Tropical House a few year back.

The object of desire is either the world's biggest cluster-of-flowers or the biggest unbranched-inflorescence (an inflorescence being a collection of flowers and associated bits and pieces). For the botanically inexperienced, or perhaps willfully radical as I'll argue, it's the world's largest flower (but see also Rafflesia).

This is our most recent bloom in Melbourne's Royal Botanic Gardens Tropical Glasshouse. It's the third time a Titan Arum has flowered for us, and the second time for this particular tuber (the first flower was in January 2013, a month after its Christmas flowering sibling). Our tubers came from Sydney's Royal Botanic Garden and their plants started as seed collected by David Attenborough and Wilbert Hetterscheid in Sumatera in 1993. The tip of the banana was 233 cm above the ground late yesterday; impressive, and closing in on the biggest recorded in Australia (Cairns had one at 238 cm in 2014), but well short of the record of 290 cm for a plant in cultivation. We expect the thing to open fully in the next few days, perhaps putting on a few extra centimetres on the way...

But what do we call this huge and impressive infrastructure, home to thousands of tiny flowers, or florets as we sometimes call small flowers of this kind? Each one consists of either a single bottle-shaped pistil (this is the stripped away female part of a female flower, including the ovary in the bottom of the bottle, a stalk called a style and a sticky blob on top called a stigma) or a single stamen (in this case a spherical sack of pollen).

None of these flowers/florets are garnished with petals. The pistils (female 'flowers') are in neat rows at the bottom and fire off together - sorry, they become receptive all at the same time. The stamens (all that there is of the male 'flowers') are packed in at the top and release pollen together. So although technically the skirted banana structure is a collection of single-sex flowers with some very fancy accoutrements, if the whole thing looks like a flower, behaves like a flower and smells like a...dead possum...let's call it a flower.

I would argue, following the lead of an expert in this family, Dr Alistair Hay, that the floral bits are so reduced as to be equivalent to organs within a larger flower and the skirt (spathe) and banana (spadix) work in the way any other flower does in attracting pollinators to the receptive parts of the flower(s). In fact the Kew Plant Glossary helpfully describes a flower as 'an axis bearing one or more pistils or one or more stamens, often with parts to make it more functional or more attractive to pollinators'.

Now of course you could argue the same way for any inflorescence or collection of flowers but, I would suggest, rarely as coherently as with the Titan Arum bloom. It certain teeters on the edge of being a flower or an inflorescence.

Maybe the solution is to give this spectacular and fascinating structure honorary flower status. I can see parallels with the debate over Pluto's planetary rank although I'm not sure it helps my botanical case to read that Pluto may soon return to full planet status after having to endure the floret-like moniker of 'dwarf planet' for the last nine years. That aside, the 'largest unbranched inflorescence in the world' is just lame.

Images: The unopened Melbourne flower, with close-up of skirt/spathe at the top, come from a stock of images taken by David Robbins, Robyn Merrett and me. The carved plant and close-ups of pistils and stamens, plus the following picture of a spent flower with its inside-out skirt looking like a breezy coiffure, I took in 2007 at the botanic garden (Keban Raya) in Cibodas, Indonesia. The open flower (!) above, with a visiting man, is from Sydney in 2008.

Feedback: Dr Phil Garnock-Jones from New Zealand suggests the term blossom. He says in a tweet (10 March 2015): "Excellent. I'd call it world's biggest blossom. Many flowers, 1 blossom; cf. an iris, with one flower, 3 blossoms" Has some merit.

And further information?: See and hear me talking about the flowering of the Titan Arum in Melbourne on 13 March 2015, with excepts from this post about whether it's a flower or group of flowers, on RN website.

Tuesday, 3 March 2015

Begging for begonias

I shouldn't say beg, it was more like a coax and persuade maneouvre (but that doesn't alliterate as well). Back in December members of the Melbourne Begonia Society encouraged me, as they should, to grow more begonias in the Royal Botanic Gardens.

I was speaking to them about plans for the Melbourne and Cranbourne sites, with a glancing mention of begonias. Apart from their regular displays they prepared a selection of the species William Guilfoyle was growing in the Royal Botanic Gardens in 1883, and presented me with a list of the same.

I was also gifted a photo album including images of everything displayed, plus a few missing species to show me the beauty and breadth of Guilfoyle's collection. On that front, I didn't take much convincing. Begonia boliviensis (sometimes called 'Begonia boliviana' in horticulture*), the species I've used to illustrate this post, is just one of the colourful and sensuous plants on the list. 

And a decade ago, after a some initial hesitancy I became a big supporter of the begonia beds at Sydney's Royal Botanic Garden, approving the expansion by Peter Sharp and his volunteers (supported by Paul Nicholson and other staff) into a second bed (photographed here at its opening in 2007).

In my talk I mentioned the possibility of a new glasshouse at the Melbourne site, the prefect place for begonias in Melbourne. Some grow outside, like the Begonia boliviensis photographed near my front entrance at home, but many more would grow under glass.

I'm surprised I haven't posted anything about begonias yet. As compensation, let me give you some fast facts from my friend Peter Sharp's lovely book, Down to Earth with Begonias.

There are around 1500 species of Begonia, and undoubtedly more to be discovered and described, so I needn't try to grow them all. They are divided up into cane-like, shrub-like, rhizomatous, semperflorens, trailing-scandent, thick-stemmed, rex and tuberous. It's beyond this post to explain the intricacies of begonia classification but for most the names are relatively self explanatory.

The rex bogonias, are perhaps not, and they are all cultivars of one species, Begonia rex, a rhizomatous species (i.e. spreading by underground stem - a rhizome) from the state of Assam in India. The wild species has green leaves with silver banding, I think, but as I saw in the extensive display in Bentleigh, the cultivars now grown have leaves of green to grey to deepest claret and purple. The leaf colour range has been compared with precious metals, and the texture with exotic fabrics.

We grew a couple of rex begonias in our front garden in Sydney, under a tree, where they more or less thrived. Here in Melbourne you'd need a glasshouse, or fish tank.

You can grow quite a few begonias outdoors in Sydney but further south (and up the mountains) it's often best to grow them in pots and protect them from frosts and very cold winters. That said, here in Melbourne the climate may be coming more conducive to growing begonias outdoors.

The best known begonias are probably the tuberous ones bred to produce big blousy flowers, of the kind you might find in the Ballarat Botanical Gardens. These you will find grown and displayed in a glasshouse.

What all begonias share are asymmetrical leaves, as in this picture of the (non-rex) Begonia boliviensis I took home from the meeting in Bentleigh.

In addition to being one of the species grown by Guilfoyle it is also from Bolivia, so I can add it to my Talking Plants list of plants from that oddly romantic country. It's a tuberous species from the cold peaks of the Andes, but happily adapts to gardens in Sydney and Melbourne, producing lovely summer flowers.

Begonias have either male or female flowers, both on the same plant, and as you can see the male flowers are quite open in this species so you can see the pretty anthers ready to release their pollen.

For now the pot sits at my front door. A reminder for when we build a glasshouse at the Royal Botanic Gardens: remember Guilfoyle, Bolivia and...oh, yes...begonias.

*Thanks Peter Moonlight for advice on nomenclature. And look out for a full census of Begonia species, coming soon according to Peter! 

Tuesday, 24 February 2015

Misplaced (and edible) hat plant

It takes six leaves from the Panama Hat Plant to make a Panama Hat. The leaves must be young and most commonly they will come from the country of Ecuador. Never or rarely, I gather, from Panama, where the hats were first traded in the nineteenth century.

The Panama Hat Plant looks like a palm. Indeed it is sometimes called the Jipijapa Palm, after one of the Ecuadorian towns that makes the hats. But it's not a palm. Botanists have always know that. In fact these days we consider it even less of one!

Carludovica palmata has always had its own family, Cyclanthaceae, but this used to be tucked in near the palm family Arecaceae, albeit each within its own order (Cyclanthales and Arecales). The Pandanas family, Pandanaceae, used to be thereabouts, again in its own order (Pandanales).

Nowadays our Panama Hat Plant is included within the Pandanales, closer to Pandanas but distant now from the true palms which are clustered elsewhere in the family tree with grasses, gingers and the water hyacinth (in a group called the Commelinids).

To look at though, the fronds look very palm-like. The one-metre wide leaves are fan-shaped, divided into three to five segments, with each segment further divided towards the tips.Unlike all fan palms, however, it doesn't produce a trunk.

The flowers arise from the base of the plant, on a stalk and grouped in a cylindrical 'spike'. As with cycads, an very unrelated group of plants, weevils pollinate the flowers.

The Panama Hat Plant is a tropical species, growing naturally from Mexico to Bolivia, but more commonly in Ecuador. In Australia it grows outdoors in Sydney and Brisbane botanic gardens, but apparently not here in Melbourne. There are three other species in the genus Carludovica, all with similar horticultural requirements.

Apart from spiffing hats, the leaves are used for 'matting, curtains, roofing, baskets, cigar-cases, purses, fly swatters and brooms'. In fact anything that needs a tough, weavable fibre, including mammal and fish traps.

In Ecuador the base of the unopened leaf base tastes similar, apparently, to a palm heart. This may be a more sustainable way to satiate that particular food fetish given that extracting the heart - the growing point - of a palm kills it.

I just need to wait until this specimen on a colleague's windowsill matures a little, then creep in and do some (sustainable) harvesting.

Image: a photo by Lynda of me with my then new Panama Hat, in London in 2012. The window sill seedling is from the office of Frank Udovicic, at the Royal Botanic Gardens Melbourne, who drew this plant to my attention. The picture of the mature plant is by Bill Baker, from Royal Botanic Gardens Kew, taken inside the Palm House at Kew Gardens by the looks of it.

Tuesday, 17 February 2015

Wiping the glaucous sheen off a Pig's Ear

In early January I kayaked past this plant spreading up, or down, the banks of the Yarra River. Then a little later in the same day, walked past it in jutting from a rock wall, leaves sheening in the brilliant midday summer sun.

It's not a plant you can kayak or walk past easily, particularly when in flower. Cotyledon orbiculata, more commonly called Pig's Ear, is grey with a glaucous sheen, almost all over. The exceptions are the edges of the leaves, which are red, and the inside of the flowers, which in this case are orange to appeal to sunbirds.

Pig's Ear flowers mostly in winter but where there is more winter rainfall, such as the Western Cape (and here in Melbourne), in midsummer. Presumably the African sunbirds know when to be active.

According to Shireen Harris on the PlantzAfrica site, there are 10 species of Cotyledon, a genus name based on the Greek work kotyledon meaning cup-shaped hollow (and also used for what are called the seed-leaves of most flowering plants, the cotyledons).

The leaves of most species, including Cotyledon orbiculata, are cotyledon-like in shape.

The waxy white coating reflects the sun's heat, to prevent overheating and water loss. In low light, little wax is produced, in high light (such as on this rock wall), lots. When fully coated, up to 50% of the sunlight reaching the plant surface can be reflected and water loss reduced.

If you remove the coating, as I did here with my finger, it will take about two weeks to start returning again on that leaf. The waxy deposits are formed inside the leaf cells and exuded to the outside during growth and after injury. It seems that the route to the surface, and the means of production, do not shut down once the leaf is mature.

(I did a slightly more thorough test  on a smaller plant we are growing at home, wiping strips from two differently aged leaves to see what would happen. After two weeks a light cover of wax had returned on both, and now, just over six weeks later, the coating is thick enough to make the strip look grey rather than green, It's still noticeable though and I wonder if it ever completely recovers its full coating.)

I doubt that in the Australian summer my interference will cause the plant, or even this leaf, to die (the cuticle, a more important waxy-outer-layer on nearly all leaves, did survive my vandalism), but is a shame to do it more often than you need to in the interests of curiosity. If for no other reason, it detracts from the beauty of the plant as a whole.

In their southern African homeland, in rocky outcrops, the plant may well be more finely tuned. One poorly performing leaf could be the difference between living and flowering, or death. Perhaps. 

For me now, there are those complex feelings after you have done some thing you really shouldn't have. I know this leaf will recover its wax but will it be in time to survive the summer? I'm not sure if it matters, given the small surface I scraped, but I do add it (along with memories of insects I've squashed, birthdays I've forgotten and chances of selfless assistance to others) to my life-time load of guilt.

But then, in Australia Pig's Ear has escaped from gardens and is spreading through bushland areas, such as the Yarra River verge near my home. If I were to think instead about the potential of this plant to jump the garden fence and spread further into native vegetation, displacing indigenous plants and animals, I could convince myself this was a (very) small contribution to conserving Australia's biodiversity.

But that would be stretching things a little (a lot). And unfair to my neighbour's garden.

Images: all from the plants growing out of the rock wall in a nearby street. 

Tuesday, 10 February 2015

Saint-Catherine's Lace covers giant island-plant

In early January I took these pictures of a striking plant among the rocks in our Californian Garden. There is another on the way into the Royal Botanic Gardens at Observatory Gate, and it was featured on the Gardens' Facebook page on 30 January. It's a rare plant called Saint Catherine's Lace, growing naturally in the Channel Islands 150 kilometres west of Los Angeles.

The Channel Islands include three large islands (plus some smaller outcrops), each with its own variety of Saint Catherine's Lace (Eriogonum giganteum). I gather this species (and its three varieties) is native only to the islands of Santa Barbara, San Clemente and Santa Catalina but you sometimes see its distribution represented as far wider in California, extending along the mainland coast from the Mexican border up to about San Francisco. I'm presuming these are naturalised records given it is so widely grown in gardens throughout the state.

Also called the Giant Buckwheat, it can grow to two metres high, and across. The Catalina Island Conservancy cites Saint Catherine's Lace/Giant Buckwheat as an example of island-induced gigantism. That is, islands acting as discrete evolutionary laboratories where plants often become unusually large, or small.

These islands are hot and dry and Saint Catherine's Lace needs little water to survive in Melbourne. It flowers over a couple of months (attracting lots of insects and birds) and looks attractive in woolly leaf for the rest of the year. Sounds like a plant that should be grown more often, particularly as our summers become hotter and our rainfall less reliable.

Just watch it though. In Californian gardens it seeds readily and self sows, so do make sure it doesn't spread beyond your garden. At the moment is so rare in cultivation that its potential to spread is probably untested. (It also has a propensity to hybridise with other species of Eriogonum but as we have no native representatives in Australia that shouldn't be a concern.)

The buckwheat we consume as a grain, by the way, is another species in the same family (Polygonaceae) called Fagopyrum esculentum. As you might have guessed, it's a smaller plant, as are other species of Eriogonum also bearing the common name Buckwheat (or more often, Wild Buckwheat). 

All these buckwheats are unrelated to wheat (a species of Triticum, and a kind of 'grass'), which accounts for the absence of gluten in their grain, making at least Fagopyrum esculentum flour a rather popular substitute for wheat flour in bread and pasta.

You could also be mistaken for thinking our plant was in the carrot family. The flowering structures (below) certainly resemble things like Queen's Anne Lace in the family Apiaceae.

As to Saint Catherine, I think she is the Catholic saint and Princess from Alexandria. She is often portrayed in paintings wearing quite elaborate garb, leading I presume to the reference to her lace*.

In mature bushes the lacework of flowers can almost completely cover the whole bush, as in this shapely specimen from the California Native Garden at Golden West College, California. This is something for us to aim for in our Californian Garden.

Images: The picture from Golden West College is from their website.

*This intriguing and slightly gruesome comment added to the blog might is a likely explanation: 

lena.m said...
Saint Catherine, princess of Alexandria, was martyred for her purity , wisdom, and persuasive powers, by being bound to a wheel where upon her limbs were to be broken, but the wheel fractured, and she was decapitated. Hence the Catherine Wheel fireworks, and white for the purity represented by her name.

Tuesday, 3 February 2015

Yuck, ah, not

What used to be called Yucca whipplei is a popular landscape plant in Melbourne's Royal Botanic Gardens. The pin-cushion clumps are ultra-neat and pastel-grey in colour. They fit nicely into our Californian Garden because that's where they hail from (south-western North America), and in our Guilfoyle's Volcano collection (pictured here) due to their succulence and tolerance of dry conditions.

Also called Our Lord's Candle, this yucca is now in a separate, less memorably named, genus, Hesperoyucca. There are two species, one named after Mr Amiel Whipple, the other after Mr John Newberry. Ours is therefore now Hesperoyucca whipplei.

The 'hespero' part of the genus name presumably refers to their western distribution in North America, and they differ from the rest of the yucca cohort in subtle details of their flowers and fruits. The leaves clasping the flower (bracts) are usually bent backwards and the receptive part of the female structure (the stigma) is 'head-shaped' rather than with three lobes (each sometimes split in two) as in Yucca. (The stalk supporting the flowers and fruits is also wider in Hesperoyucca than in Yucca.)

None of ours are in flower at the moment so here is what they don't look like! These are images I took of a Yucca (not Hesperoyucca) flowering in a street near my home. Note too the very cool anthers, looking like pipe cleaners tipped with a blob of gold paint (the pollen).

I got excited a few weeks ago when a succulent which seemed to be labelled as Hesperoyucca started to flower in the California Bed. It produced a massive flowering stalk, much bigger than I was expecting. And that because it was an agave (same family but quite different). The Hersperoyucca whipplei had died recently, so the sign seemed to the untrained eye (sigh) to refer to the next door agave. Clearly a lapse in my botanical logic given the agave had whopping great thick leaves and the flower-buds were, not surprisingly, starting to look more like an agave than a yucca...

So you don't get any pictures of the Hesperoyucca flowers I'm afraid. Or any discussion about what, if any, variant of Hersperoyucca whipplei we might be growing. Sometimes Hesperoyucca whipplei is split up further into subspecies or varieties based on the way they produce 'offsets' (the plants that bud off at the base, surviving the death of the main clump after flowering) and the size of clump and flower spike.

I'm not sure where to go with the common name Our Lord's Candle. I'm tempted to say I won't touch it. Instead let me tell you it refers to the candle-like flowering structure, with hundreds of white typical-yucca-like flowers.

The flower-less plant is pretty enough, but do take care. Each leaf is terminated by a sharp pungent point. The finely toothed margins (which you can almost make out in this next photograph if you squint a little) you needn't worry about. At most they gently massage your finger-tips.

Each cushion takes about five or more years to flower, then like the agave (in the same family and subfamily) it dies, with off-shoots from the base taking over to run through the same cycle again. In its native California a moth pollinates the flowers at night, contributing a small moth egg as well as pollen to the receptive flower. This egg grows into a larva that will eat some, but not all, of the seed.

Here in Melbourne, without the moth, we may not have any problem with caterpillars eating our seed, but then we may also not get any seed. Which, according to this sign, means ropes, nets, baskets and soap, but no flour.

Tuesday, 27 January 2015

Eel heads and floating flowers

All seems calm at the Ornamental Lake in Melbourne's Royal Botanic Garden. It's a wintery morning before a hot summer's day in late January. Fairly typical weather for this city.

There are a few (sub)tropical trees still flowering but the Jacarandas, Brachychitons and Cape Chestnuts have finished. Recent rain has kept the Gardens green but you can sense that things are about to curl and brown, with most plants shutting down for the summer.

In the lake itself there is plenty of algae, mostly submerged clumps of a green alga called Spirogyra, which do from time to time float to the top. The Purple Loosestrife (Lythrum salicaria) continues to do what it does best on the floating islands - bloom, bloom and then bloom some more.

In front of this floating wall of grass and loosestrife you can see mats of algal and aquatic plants accumulating at this north-east corner of the lake. The dominant aquatic plant is Eelgrass, Vallisneria australis, a Victorian native that extends all the way up to near the Queensland-New South Wales border. There are seven or so species of Vallisneria in Australia, mostly tropical, and mostly with long ribbon-like leaves - hence the common name.

For most of the year you can just ignore it. Eelgrass is there, doing all kinds of good things in the lake in terms of habitat and nutrient recycling, but for you and I its a case of move along, nothing to see here.

But in late January something does happen. The first thing you might notice are tiny eel heads poking up out of the water. I say eel* heads but that's just me being poetic and metaphoric. These are the, by the time I got to see them 'spent', female flowers.

The next thing you (might) notice is an intricate lacework of white fluff. These are the male flowers.

As you will have gathered, this is a plant with single-sex flowers. That's not unusual per se in the plant world but the way these flowers work is. Eelgrass has a particular method of pollination called, entirely unhelpfully, ‘Type III’. It's only found in Vallisneria and other members of its family Hydrocharitaceae.

The key feature is the complete detachment of male flowers as buds from a sheathed stalk at the base of the plant. These tiny flowers float to the surface where they open fully and then coagulate together in floating rafts, drifting around with the wind and current.

There are minor variations to 'Type III' pollination, and in Eelgrass and two other related genera, the pollen has to remain dry. So the flowers actually float so that the pollen bearing bits are held aloft, above the water! You see them here hovering around a slightly submerged eel head, a flower already fertilised and having lost its petals (and sepals).

The receptive part of the female flower (the style) also has to remain dry, before fertilisation. At first the style is protected by the tightly wrapped petals (and sepals). By the time the flower opens, its long flexible stalk has extended it through the water surface. There it eventually comes in contact with the drifting male flowers and fertilisation takes place.

All the female flowers I saw and photographed were fertilised and beginning to set seed. After pollination the stalk of the female flower becomes spiralled, dragging the developing fruit underwater. The seed are eventually released in the murk beneath, to be washed around and settle somewhere new.

Yes really. That's what is going on in and on the lake while the rest of the garden is bunkering down for late summer.

* As our website boasts, the Ornamental Lake is home to a healthy population of Short-finned Eels (Anguilla australis). These eels live hereabouts before the arrival of Europeans, and they enjoy the moderately shallow parts of the lake where they feed on crustaceans, frogs, insects and worms. So much so that they can reach 1.3 metres long. Eventually though they swim and slither their way into coastal estuaries where they swim 4,000 km to spawning grounds in the South Coral Sea. Because eels can breathe through their mucus-coated skin, they can in fact slither overland when it's damp (e.g. at night). At breeding time the mature eels are drawn towards flowing water, and find their way through drains to the Yarra River. The leaf-shaped larvae (soon becoming what we call 'glass eels') hatch off New Caledonia and are carried southwards on ocean currents, until at the age of one to three years when they (now 'elvers') migrate up Victorian rivers and streams, until some call our Ornamental Lake home. 

[Thanks to Neville Walsh for directing my attention to the curious botanical phenomenon.]

Tuesday, 20 January 2015

The sweet aftertaste of artichoke

There are lots of phenolics in Globe Artichokes. To be fair, there are lots of phenolics in the plant kingdom more generally. Phenolics are, in chemical terms, compounds with one or more of what chemists like to call 'aromatic rings' and with one or more of what chemists like to call 'hydroxyl groups'.

[The simplest aromatic ring is the one with six carbons and six hydrogens, drawn as a hexagon with every second side with a double line. A hydroxyl group is represented as an O (oxygen) with an H (hydrogen) sticking off one side and the hexagon or something similar off the other.]

Phenolics are produced by most plants as secondary metabolites, that is products not used directly for growth or reproduction, but for things like protection against pests, against excess radiation or add colour to various plant parts. So far we know of 8,000 different phenolic compounds in plants.

Phenolics add some of the more interesting flavours to fruit and vegetables, such as the bitterness and astringency of berries, and give tea, coffee, beer and wine their kick.

One of the phenolics in the Globe Artichoke is called cynarin. It inhibits taste buds that detect sweetness. And as you eat other things afterwards, the cynarin layer in your mouth is gradually removed making everything suddenly seem very sweet. Miraculin does the same thing in the so-called Miracle Fruit.

To test this I went to my local shops to find a fresh Globe Artichoke. Sadly, none to be found. So I thought I'd test a grilled and pickled version, to see if the phenolics survive all that processing.

Turns out they don't. At least in the one I tasted and then followed by a lime. I ventured further afield and eventually found some fresh artichokes (below) which when eaten after boiling caused water to taste a little sweet (although the sweetness emerged a few minutes later) and very slightly made a lemon seem less sour (not exactly sweet, although again, a few minutes later I could taste sweetened lemon in my mouth). Not quite as miraculous as Synsepalum dulcificum, but a little bit fun.

By the way, the artichoke I'm talking about here is the Globe Artichoke, a thistle, Cynara cardunculus (you can see where the phenolic name comes from). The Jerusalem Artichoke, Helianthus tuberosus, illustrated below, is also in the daisy family but not a thistle and more closely related to the Sunflower (Helianthus annuus). And of course rather than the flower head, you eat this, the tuber.

And not all Cynara cardunculus are Globe Artichokes. While there is some debate over what names to use, there are usually two subspecies recognised, one for the Globe Artichoke, the other the Cardoon (it again is usually divided into two varieties, the cultivated and the wild Cardoon).

The Cardoon is also eaten, and was described recently as 'a fantasy dragon of a vegetable: what celery would look like it went through the Looking Glass and ended up in the Game of Thrones' (do check out the photograph in this link - you'll soon get the idea). They taste a bit like artichokes but you eat the stem rather than the heart of the flower head.

 Thanks to Janet O'Hehir who many months ago mentioned this characteristic of the Globe Artichoke to me after I wrote about the Miracle Fruit. And the beautiful drawing of an artichoke, Cynara cardunculus var. fortissima, is by Debra Bartlett. It was bought last year by the Royal Botanic Gardens Melbourne Director's Circle for the State Botanical Collection, and resides at the moment on the wall in my office. (I can't track down this varietal name but presume it is a Globe Artichoke.) The flowers photographed are in front of the Alpine House at Kew Gardens in 2011.