Tuesday, 27 September 2016

Clive of Syon Park

Did you, like me, think that the popular orange-flowered bulb Clivia was named after Robert Clive, aka 'Clive of India'? I've been promulgating this lie every time I explain to someone why Clivia should be pronounced with a long, rather than short, i (as in bright rather than brilliant)

As it turns out - and thanks Michael Barrett (President of the Melbourne Clivia Group and key organiser of the Clivia Expo 2016) - the genus was named after Robert(Clive of India)'s granddaughter, Duchess Charlotte. Thankfully the pronunciation remains the same.

Lady Charlotte Florentia Clive was Duchess of Northumberland, spending her springs and summers across the Thames from Kew Gardens, in Syon House (in Syon Park).

She was Princess Victoria's State Governess, appearing with Victoria on official occasions but apparently doing little else to educate the future Queen, partly due a fear that she might subvert the young mind (to horticulture perhaps?). The Duke and Duchess had no children but Charlotte - with some help from her gardener Richard Forest - was a dab hand at keeping cliveas alive in the conservatory at Syon House.

I've featured Syon Park, the surrounds of Syon House, before, but at night. Here is what it looks like from across the Thames, standing in Kew Gardens. You can see the lion which notoriously faces its backside towards Windsor House.

Lady Charlotte grew her exotic plant material in the Great Conservatory, still there today and carefully restored 30 years ago. I captured it somewhat obscurely in this picture from my night time visit in 2011.

In their homeland - coastal and inland forests of southern Africa - the five or six species of Clivia grow mostly in cool, shaded habitats. A species discovered in only 2002, Clivia mirabilis, is the exception, frequenting semi-arid areas with winter rather than summer rain.

You can find out more about the discovery, ecology and horticulture of this genus at the Clivia Society website or in an article by Graham Duncan in the latest issue of Curtis's Botanical Magazine (including extensions to the natural range of Clivia miniata in southern Africa).

In both accounts you'll learn that James Bowie, collector and gardener at Kew Gardens, sent the first horticultural material back to England in the 1820s where it made its way across the river to Syon Park. It was there the first flowers were produced and sketched, forming the basis of two botanical papers published on exactly the same October day in 1828. John Lindley's name Clivia has been given priority over Imatophyllum, the name coined by Director of Kew Gardens, William Hooker.

That species was Clivia nobilis (or Imatophyllum aitonii in Hooker's paper), but the orange-flowered plants that feature in botanic gardens and other grand gardens across Australia today are mostly cultivars of Clivia miniata. This second species found its way to England in the 1850s, although it took a decade or so for botanists to realise it was closely related to Clivia nobilis and should therefore carry the 3rd Duchess of Northumberland's surname.

And to correct another misconception, clivia flowers are not always orange. You might have seen the occasional yellow-flowered form but they can also be creamy white, red or even green. New colours and infusions continue to be created through breeding, including picotee forms (a term used mostly for carnations and tulips with dark tipped petals) such as the sorbet coloured bloom at the top of the post - a Clivia miniata cultivar, a cross between 'Electra King' and 'Tango'. Also at the very top of this post is a clump of regular Clivia miniata doing very nicely at Burnley Gardens.

Then there are doubles, with extra petals, and to my horror, variants with variegated leaves (I have a thing about variegated plants).

Here are a few selections from Saturday's Clivia Expo, with Michael Barrett featuring in the first, along with one of the famous yellow forms of Clivia miniata (sometimes called var. citrina).

This is one of your fairly typically shaped and coloured Clivia miniata flowers.

This next flower is more typical of the genus Clivia: all but Clivia miniata have pendent flowers. It's a cross between a natural Clivia caulescens and Clivia miniata hybrid and the more arid tolerant Clivia mirabilis.

 And finally, this creamy green one is Clivia miniata 'Hirao'.

Tuesday, 20 September 2016

Beautiful noxious weeds

No I'm not going to rant and rave about how weeds are 'plant' - like you and I if we were plants - or that we should embrace floral diversity and not exclude species from elsewhere. I've done that before and in any case I'm as patriotic (not nationalistic I must add) as the next botanist when it comes to our cute and curmudgeonly Australian flora.

Today I want to celebrate the beauty and personality of a few noxious species, through the beautiful paintings of Elizabeth (Betty) Conabere. Conabere was born in Mansfield in 1929, and died there in 2009. In an obituary in The Age and The Sydney Morning Herald written by Janet McKenzie, Conabere is described as 'outspoken', 'outrageous', 'larger-than-life', 'contentious', 'provocative' but also 'generous', 'passionately opposed [to] injustice' and even (second hand) 'sumptuously beautiful'.

Many of these adjectives apply equally well to her paintings, particularly those commissioned by the aggressively named Vermin and Noxious Weed Destruction Board for the series Beautiful Noxious Weeds. That set of beautiful water colours now resides in the State Botanical Collection at the Royal Botanic Gardens Victoria, after touring the State in the 1970s and then being stored at the now-no-longer Keith Turnbull Research Institute.

I've only included two images from the collection, taken in haste as the collection was sorted before cataloguing and storing. The Serrated Tussock (Nasella trichotoma) is hard to resist - hated with a passion, costing the NSW government around $40 million a year to control, but rather delicate and charming in this composition.

The image at the top was chosen for its evocative common name, Apple of Sodom. Even its botanical name, Solanum sodomeum, references that famous biblical city but due to the vagaries of botanical nomenclature it is now called Solanum linnaeanum (after Carl Linnaeus, the Swedish botanist who established this system and the rules we still use today).

Sodom was apparently home to some plants that produced very bitter apples indeed. This particular bitter apple, a member of the family that brings us deadly nightshade but also potatoes and tomatoes, is a small shrub with spiny stems and leaves. It's native to African and the Mediterranean but now weedy throughout the world, including all most parts of coastal and near coastal mainland Australia except for the far north.

Apple of Sodom was first detected near Sydney in 1802 and by 1895 it had become a noxious weed in Victoria, then two years later in South Australia. It's also now listed in Tasmania (where it is prohibited and possibly excluded or at least kept under some control) and Western Australia. We don't like it because it competes with native species, crowds out pasture grasses (it is not grazed itself), provides a home for rabbits and snails, and its fruit is toxic to 'children and sheep' (although due to its spines it is not often eaten).

That said it is a medicinal plant in South Africa, used for a ailments such as skin disorders, toothache and colds. The roots are carried, it is said, as protection against poisoning. Farmers also use the above ground parts to treat skin problems in stock and it may well be on future benefit in treating skin cancers. So it is both good and evil.

Before Conabere turned to the dark side (although I should point out Conabere was a passionate conservationist and by no means advocating the acceptance of noxious weeds), she was commissioned by the Royal Botanic Gardens Victoria to paint about 50 Victorian alpine plants, which we already hold in the State Botanical Collection. Her best known work is perhaps in Wildflowers of South-eastern Australia, published in 1974, with text provided by Ros Garnet. The originals for this publication are held in Melbourne's La Trobe Library and all subjects evolved and dispersed more or less in situunabetted by humans.

Tuesday, 13 September 2016

Don't snort the autumn-winter-sprinter daphne

This Winter Daphne has been flowering since we moved into our home in April. By my reckoning that's an Autumn, Winter and now Sprinter Daphne. You see it described as flowering in mid to late winter and early spring, which is about right, but not a great basis for a common name.

Daphne odora is an enduring plant. It survives in a dull little corner in our new backyard as it does throughout Melbourne and the greater universe. It smells, a little - we debate here about just how much perfume it produces and this seems to depend on your 'nose'. Sometimes the perfume is described as delicate, which seems about right.

Oh and most parts of the plant - particularly the bark and berries - are poisonous so take care when handling, and please sniff rather than snort. Just a few berries = death of a child.

The species is usually described as native to China, where if flowers from March to May (mid-sprinter to mid-sprummer, or just plain old spring - not winter), but in the Flora of that country it is described as being of obscure natural origin: 'probably China or Japan'. You also see Korea mentioned in dispatches.

We have one of the green-leaved, pink-tinged-flowered forms. The flowers are small but the the port-wine colour of the buds, later flushed through the petals are attractive, is nothing to be sneezed at.

The shrub is about one metre high and thrives on neglect (in a cool, sheltered, east-facing position...). You read about them turning up their roots now and then but this one was obviously well established at some time and seems to be with us forever ...  or at least the 8-10 years life span usually quoted for this species.

It's a plant for the cooler parts of Australia, and perhaps London... Many of the daphne species are actually native to the Mediterranean region. We had a local UK one, Daphne laureola, by our back door when we lived in London, inside Kew Gardens. Sadly it had been hacked back before we arrived and we ended up removing it almost entirely due to its inability to return to anything resembling an attractive habit.

Somewhat gratuitously (and you know I like doing this) here is the back of the house at Kew, and a close up of the back door. You can see the daphne stump in the second picture, surrounded by replacement plantings. I can't recall if it sprung back to life or not, but perhaps it too had life span of around a decade.

Tuesday, 6 September 2016

Trim and attractive to gnats

A couple of months ago I spoke to the enthusiastic volunteers who run the plant nursery of the Friends of Warrandyte State Park (or FOWSP as they like to be called). I spoke to the Fowspians about the kind of seasons I'd like to see in Australia. Not changing the climate itself - others are doing that more effectively - but how we might better reflect our local climate with seasonal names and durations.

My plan, as I'm sure most of you by now, is to swap the Vivaldian seasons for sprinter (August to September), sprummer (October and November), summer (December to March), autumn (April and May) and winter (June and July). We are now in mid-sprinter - Australia's early spring - and already wattle flowering has peaked in much of southern Australia. The native orchid season is well advanced, although there are many waves to this flowering cycle.

While talking up my seasons in Warrandyte, I was reminded of the very similar Middle Yarra seasonal calendar, started by Alan Reid, adapted by Glen Jameson and later further fine-tuned by Beth Gott taking into account local Indigenous knowledge. The reminder came in the form of a box of giant yearly calendars marking off the six seasons, and the presence of Glen himself in the audience!

So for at least some in the audience I was telling them what they already knew, with a little extra vocabulary (sprinter and sprummer in particular). In thanks for doing this I received this bowl of greenhoods, a group of mostly winter and sprinter orchids (almost entirely winter-sprinter I think if you support separating out particular greenhoods such as this one into their own genus - see below...).

My talk was in late July - winter in both Vivaldian or Entwislean systems, although 'deep winter' in the terminology of the Middle Yarra. The greenhood was Pterostylis concinna, illustrated here a few days later at home.

I include the time scale because between the talk and home the pot upturned. The flowers and their basal leaves, and their roots and tubers, all lay beneath a pile of potting mix on the floor of my car. I resisted the urge to grind the tubers into flour, and mix myself a brew of salep (or sahlep; something I must - I will - post on in its own right), a Turkish drink that should perhaps never be drunk due to its impact on rare local orchid species. Instead, back at work I picked up the pieces and replanted most of them. Surprisingly, they survived the turmoil and continue flowering in my backyard (although they are now in their final days)

And so why do these flowers look like they do? Their common name is Trim Greenhood, and even after their disruptive car journey they remained just that - trim and neat, and with a green hood. The species name concinna is Latin for neat. It's a common enough species in Victoria, and one that is hanging on in the outer suburbs of Melbourne (e.g. Warrandyte).

One of the outer layers of the flower (sepals) and two petals are fused into a hood - the 'greenhood' - and the other two outer layers are fused into a kind of bib at the front with a V-shaped notch flanked by two brownish whiskers. Inside there is another petal which is called the labellum or lip, with its own mini V-shaped notch.

This all works as a trap for gnats who then have to crawl out past pollen grains (not in a sticky mass called a pollenia, which is found in many orchids) and the receptive female part of the flower. If all goes well for the Trim Greenhood the insect visitors take pollen from one flower to another.

Some authors like to call this species Taurantha concinna, considering the greenhoods to be more than one genus and this particular one (the 'Bull Orchids') including those with no side gap between the hood and that bib I talked about, and a relatively broad lip with that mini-notch.

Whatever you like to call them my pot of greenhoods, an ecosystem disrupted in transit, was successfully relocated from the Middle to Lower Yarra, remaining trim and gnat-attractive right through to middle sprinter.

If want to grow plants sourced and propagated from the Warrandyte State Park area, the nursery is somewhere you might visit on a Thursday morning (9.30 am to 12.30 am) or the first Saturday and Sunday of the month (9 am to 1 pm on Saturday, when you can also drop in at the Warrandyte Market or 2pm to 4pm on Sunday).

And thanks for my cousin Peta, and partner Jason Patton, for the invitation to talk!

Tuesday, 30 August 2016

Knotweed looks like cure for centipede bite

Centipede Plant, Tapeworm Plant or Ribbon Bush. Take your choice - we use Centipede Plant in the Royal Botanic Gardens Victoria. All of them are apt although I think it looks more like a tapeworm myself (having never actually seen one I must admit).

Its scientific name is Muehlenbeckia platyclada. The species name 'platyclada' is pretty good too, with platus old Greek for broad and klados a branch or twig.

Although at times Centipede Plant has been included in its own genus Homalocladium - due largely to it's distinctive jointed and flattened green stems - the work of Tanja Schuster (currently the Pauline Ladiges Post Doctoral Fellow at Royal Botanic Gardens Victoria and The University of Melbourne) and colleagues from Sydney (Hi Karen Wilson!) and the USA has demonstrated it sits comfortably in Muehlenbeckia.

The old genus name 'Homalocladium' means smooth branches and the current one, 'Muehlenbeckia' honours Henri Muehlenbeck, a early nineteenth century French doctor who had an interest in plants.

There are about 19 species of Muehlenbeckia, all from the southern hemisphere: South America and various small and large islands in the South Pacific, including Australia with 11 species. This one is native to New Guinea and Solomon Islands.

It has an unmistakable form. The flat, jointed stems (when mature) do most of the heavy photosynthesis lifting with the arrow-shaped leaves sparse at the best of times and falling before flowering. While usually an unruly tangle of a bush I gather it can be coaxed into a hedge.

The flowers are small and white or green, and the berries smallish and red.

If you are familiar with other Muehlenbeckia species, the small flowers and berry-like fruits, and the simple tangled construction won't be a surprise. There are six species in Victoria, one possibly extinct and most quite rare within the State*. Muehlenbeckia adpressa, the Climbing Lignum, is the most common and found in nearly all coastal areas as well as the Grampians - it's a twining plant with larger untidy leaves.

More familiar might be Muehlenbeckia complexa, from New Zealand, which is sometimes called Maidenhair Vine - it has small circular leaves on wiry stems that can successfully obscure old fences and backyard rubbish (leading to alternative common names such as Mattress Vine and, in the UK, the geographically challenging, Australian Ivy). Although tending to weediness and established in native bushland in Western Australia, it seems to only persist only around old gardens in Victoria.

Centipede Plant itself is a little weedy in New Zealand, but then what isn't! And to be fair is seems to be limited in distribution. It has however become more of a problem in tropical areas of Asia and South America and in the latter seems to have been incorporated readily into traditional medicine where it is used to heal wounds: controlling pain and inflammation, and killing infecting bacteria. Various studies over the last decade have demonstrated the presence of active medicinal compounds in the stems and leaves of this species, at least some of those plants sourced from South America.

As non-subscriber to the Doctrine of Signatures, I'm less convinced by its reputed application specifically to bites by centipedes, except in the sense it would work on any break, inflammation or infection to the skin. You may as well recommend that it be ingested to expunge a tapeworm (don't do this by the way, it's undoubtedly poisonous), or somehow be applied to the unknotting of a particularly tangled ribbon (although as also a member of the knotweed family, Polygonaceae, it could just make things worse..)

*Neville Walsh (30 August 2016) informs me that the 'possibly extinct' species, Muellenbeckia gracillima, was in fact rediscovered near Cann River in 2002. 

Tuesday, 23 August 2016

Blueberry with greenflowers

I was waiting for these flowers to open before photographing them, then realised this seems to be as good as 灯台越桔 gets.

灯台越桔 is the common name given to Vaccinium bulleyanum in the Flora of China, and that species determination is also as good as we can get for this potted plant in our Melbourne Garden nursery.

Our horticultural botanist Roger Spencer isn't entirely happy with the way the blueberry genus Vaccinium is separated from others in the heath family Ericaceae, nor for that matter what distinguishes this particular species from things like Vaccinium venosum

All 450 or so species of Vaccinium have small cylinder-like or urn-shaped flowers, not as showy as the Papua-New Guinean species from the same family I featured a few months ago but often more so than this!

The blueberry you eat, or don't eat, is usually from Vaccinium corymbosum but a handful of other species also produce fruits we would call blueberries. Cranberries, should you eat them, typically come from either Vaccinium marcocarpon (in America) or Vaccinium vitis-idaea (in Europe).

Only 52 of the Vaccinium species are native to China, where this plant was collected by Bob Cherry in 2012. So that narrows it down a little.

Based on advice from a botanical visitor some time ago we had originally filed this specimen under Vaccinium kachinense but that species doesn't have leaves with these jagged edges, or arranged in an apparent whorl of 7 to 10 like this one.

That number of leaves remains a problem when we look at the other 51 species. According to Roger, the couplet in the identification 'key' asks us to choose between 5 to 6 or 9-10. If you head down the latter pathway other characteristics don't make sense, so for now we are assuming we have slightly innumerate Vaccinium bulleyanum which typically at least has leaves in whorls of 5 to 6.

Roger concludes that his identification is 'dubious', based on information to hand, but the best we can do for now. If it is indeed this species, it hails from shaded mountain valleys in the west of Yunnan province. 

It was described in 1912 by Friedrich Diels, in the journal of Royal Botanic Garden Edinburgh, as a species of Agapetes, a related small genus of mostly climbing plants. The description was based on material collected by the Scottish botanist George Forrest in 1905, and the number of leaves per whorl is not specified.

Forrest named the species after his patron, Arthur Bulley, who ran a nursery and public garden in Ness. Whether Mr Bulley appreciated being honoured by this drab-flowered species, I don't know.

Tuesday, 16 August 2016

A six-headed literary monster (Plant Portrait XIV*)

One of my subscription podcasts, Frank Delaney's Re: Joyce, is a reading and explanation of James Joyce's Ulysses in more or less weekly installments over 10 or so years. Delaney can be pretentious, mawkish and a little tiresome in his delivery but it's worth persisting with if you love Joyce and his perfect order of words.

In mid-June this year Delaney began dissecting chapter/episode nine, 'Scylla and Charybdis'. In the original Ulysses story, by Homer, Scylla is a six-headed monster and Charybdis is ... a whirling maelstrom. Transferred into Joyce's story, according to experts, the two monsters become philosophers, and we listen to a tussle between the idealised forms of Plato and the pragmatic logic of Aristotle (in this text represented by one of the heroes, Stephen Dedalus). It's about rhetoric, borrowing the super power of both Homer's creatures - their ability to persuade with words.

Anyway, I'm listening to Delaney read this chapter and tell what he thinks it means. On hearing the word Scylla I immediately of course thought of the plant genus Scilla. And then wondering if there was a genus called Charybdis. Which it turns out there is, sort of. Plant relatives of Scilla, as well as a group of marine custaceans, have been called Charybdis (like modern-day China and Hong Kong, biological nomenclature is one country and two systems, allowing the multiple of genus names).

The plants once called Charybdis are now included in Drimia, a genus grouped together with Scilla in the a subfamily (called Scilloideae) in the family Asparagaceae. This is all part of the recent reclassification of lilies and the like so it might sound a bit odd (like the siren call of a sea creature from a Mediterranean island perhaps). It used to be in the Hyacinthaceae, linking it to garden plant you'll know.

Scilla and what were once called Charybdis include bulb-forming species from Africa and around Homer's sea, stretching through to Asia. But not to South America. Yet words can persuade us differently. This is Scilla peruviana, growing in the shadow of the mountain photographed (2008) at the top of the post.

Despite the name the mountains are not in Peru, but in the south of Spain, in the Sierra del Pinar. I gather from Wikipedia that Carl 'father-of-plant-nomenclature' Linnaeus was apparently given specimens from Spain that arrived on a ship called 'Peru', leading him to mistake its origin.

Scilla was known to the Ancient Greeks as Skilla, which the Romans turned into Scilla, then Squilla. Our friend Linnaeus punted for Scilla, although again botched things up a little, requiring some later tidying up of the appellations. The flowers of Scilla have six each of the various parts but whether the flower is name after the monster or the monster after the flower, I don't know.

And speaking of places where things may or may not have occurred, the island of Madeira may or may not be Circe, which Homer refers to in his tale and Joyce uses as his informal name for chapter/episode fifteen. I've posted before on the giant quill of Madeira, Scilla madarensis, including the following picture of Graham Ross and me next to one at Kew Gardens in 2012.

Frank Delaney won't get to this point in the story for another year or two.

*Occasional posts are called Plant Portraits (in brackets after the blog title and marked with an asterisk). These are usually about things other than, but including at least passing reference to, plants. Often they will be inspired by a book or something else in my cultural life. The idea is borrowed (very loosely and with due deference) from Milan Kundera's 'Novels, Existential Soundings', in his Encounters. These essays were as much, or more, about things other than the book being reviewed.

Tuesday, 9 August 2016

Restrained sunflowers reveal internal clock

It's official! The flowering head of a sunflower arcs during the day in response to its own internal clock. No longer do I need to stare at sunflowers and ponder, as I did in 2009.

It's been known for at least a century or more that young sunflower plants (with their flowerheads unopened) track the sun from it rising in the east to its setting in the west, then get themselves sorted overnight so they can do the same the next day. Once the giant yellow flowerhead opens, it stops moving about and faces east. But why and how?

University of California study published in the journal Science sets the record straight. Helianthus annuus has a circadian mechanism, or 'internal clock', behind its solar tracking, and then some internal signalling to position its mature flowerheads eastward. This combination leads to more vegetative growth and improved pollination.

The solar tracking is caused by different growth rates on the sunny and shady side of the stem. During the day the cells on the east side grow a little faster than those on the west, and then vice versa at night.

Postdoctoral fellow Hagop Atamian and colleagues at University of California in Berkeley,  tested plants in pots, growth chambers and in paddocks. Somewhat cruelly - if you think all this makes a sunflower sentient (which as it happens, I don't) - they staked some plants so they couldn't respond at all. Others were turned around each day to disorientate them.

The stalked plants grew less than those that could track the sun. If the light source was kept static (in growth chamber) the plant swept east to west for a few days, then stopped. This, they say, 'is the kind of behaviour you would expect by a mechanisms driven by an internal clock'.

If the played around with the length of the day they found the plant lost its rhythm at 30 hours, so the cycle has some constraints like a clock rather than just responding directly to daylight and the sun. Light is the primary driver for growth, but there is an internal clock (a circadian rhythm) controlled to some extent by the direction of the light, that causes the solar tracking.

This all stops when the elongation of the stem stops and the best orientation for an open flower is facing the morning sun - 'eastward-orientated flowers are warmer than westward-orientated flowers' - and warm flowers attract bees (five times as many when the flower faces east).

All this is controlled by genes and signalling chemicals called auxins (for more of the gory micro-detail, track down those references above). For those of you worried about the poor experimental plants constrained to face west every day, the researchers found that a portable heater quickly brought the pollinators buzzing back.

Images: sunflowers from Observatory Gate display in December 2014, plus the middle one from the beds near the National Herbarium of New South Wales at Royal Botanic Gardens Sydney a few year back.

Tuesday, 2 August 2016

Neither palm nor lily

The commonly grown Palm LilyCordyline australis, is, somewhat surprisingly perhaps given its species name (although austral just means southern) from New Zealand. We also call it the Cabbage Tree, not the Cabbage Tree Palm, which refers to Livistona australis, a true palm and truly from Australia.

The species illustrated here is Cordyline petiolaris, growing in the Australian Garden at Cranbourne Gardens. This Broad-leaved Palm Lily is from coastal and near-coastal parts of northern New South Wales and southern Queensland.

All up there are about 20 species of Cordyline eight from Australia. There are many in cultivation, including some brightly coloured cultivars, and they are tough plants as long as you don't have frosts. For more on how to grow them and the horticultural forms, check out the International Cordyline Society website.

But what kind of plant is this Palm Lily? Well, it's neither a palm nor a lily (or a cabbage for that matter). It sits in the family Asparagaceae, with things like ... yes, asparagus. To be fair, most things in this family were once included in the Liliaceae, which is where true lilies reside.

The Palm Lily's cluster around the Mat Rush Lomandra and you sometimes see it put in the family Lomandraceae. Or Agavaceae (with Agave). Or Asteliaceae (with the Pineapple Lily, Astelia). Or Laxmanniaceae (with the Wire Lily, Laxmannia).

Or Dracaenaceae, with Dracaena, including the Dragon Blood Tree and other common ornamentals. Sometimes Dracaena and Cordyline get confused but scratch below the surface (of the soil) and you can tell them apart - Dracaeana has orange roots, Cordyline white.

Anyways, today the DNA tells us Cordyline is best included in Asparagaceae. This giant asparagus might look like a palm from a distance but close up  you'll see it doesn't have the single crown of leaves and the compound (feathery or fan-shaped) leaves pleated down the middle when young. And flowers, molecules and other bits and pieces are different.

While the flowers and fruits are not stalked, abutting their common stem (distinguishing the Broad-leaved Palm Lily from some of the cultivated exotic Cordyline species), the leaves have long stalks - or petioles - as celebrated in the species name 'petiolaris'.

In its native rainforest or wet eucalypt forest the Broad-leaved Palm Lily will reach five metres tall, but in most gardens it tends to settle at something like two metres; I suspect those at Cranbourne Gardens will seek greater heights, if we can offer them a little protection.

As to those gorgeously red berries that look like they'd make a fine jam or pie. I gather the giant moas in New Zealand ate the fruit of Cordyline australis, as do various non-extinct birds today. The fruits of Cordyline petiolaris are described as 'edible' and also 'eaten' but the interweb isn't awash with recipes for humans (or birds). More usually it's the leaves and roots of Cordyline that are eaten.

Tuesday, 26 July 2016

Australia's Black Wattles a flight hazard in China

Australia's Black Wattle may soon become a problem for planes flying through China. Not because the trees will grow tall enough to interfere with flight paths, but because they rather like growing in airports and birds like to roost in them.

We grow Black Wattle (Acacia mearnsii; not the unrelated Callicoma serratifolia which New South Welshman tend to call Black Wattle) in the Australian Garden at Cranbourne Gardens (above) as a quick growing screen for other plantings - in this case, with other wattles, in the Gondwana Garden.

Scientists in China, however, are worried that our Black Wattle is spreading so quickly through open landscapes such as those surrounding runways, that it may soon be a problem for aviation and local biodiversity. The airports are in Yunnan Province, in the southwest of China, including the Kunming Changshui International Airport (below, by Min Liu) where many Australian botanists and plant collectors have arrived to help document and bring into propagation Chinese plants.

Wattles have been planted deliberately in many countries to to improve soil (like most legumes, wattles bringing with it bacterial nodules that fix nitrogen and make it available for other plants and organisms), and for timber, adhesive and tannin production. 

The bark of Black Wattle contains a chemical useful for tanning leather and has been grown for this purpose in places such as Brazil, China and many South African countries. In fact the extracted tannin is exported back to Australia.

That's all good but the Black Wattle is also in the top 100 of the world's worst invasive alien species. The seeds are notoriously long-lived, and spread by rodents and birds, and often locals moving the plant around for firewood. Black Wattle is fast growing, 'fixes' its own nitrogen, doesn't mind a bit of salt in the soil and likes growing in disturbed areas.

The native (largely non-human assisted) range of Black Wattle is southern Australia - from around Hobart through to half way up the New South Wales coast - and its human assisted range now extends to Western Australia, North America, South America, Asia, Europe, Pacific Islands, Africa and Europe. In fact, as Neville Walsh reminded me (based on his memory of a discussion with Jim Ross, ex-South African and ex-Chief Botanist at Royal Botanic Gardens Victoria), the species was named after an American collector, Edgar Mearns, who found the plant growing in Kenya and other parts of East Africa in 1909.

Time for a breather. To refocus at a finer scale for a moment, if you are trying to separate Black Wattle (top picture above) from Silver Wattle (Acacia dealbata; bottom picture) look closely at the fern-like leaves. Black Wattle has green rather than silvery leaves - it is sometimes called, helpfully, the Green Wattle.

Black Wattle also has a different arrangement of raised 'glands' (the pimples with dots in the pictures above). You find them at or near the feathery leaf junctions as well as in between some of them. Be careful though. The number of in-between glands is variable, and sometimes there are none. Helpfully though compared to the Silver Wattle the glands in Black Wattle tend to not line up as well with the feathery off-shoots.

Now, back to China. It isn't so much that the Black Wattle will grow close enough to the runway to irritate pilots on take off and landing, although that must be one concern. The main problem, it seems, is an increase in 'bird strikes' (i.e. birds getting sucked into bits of a plane where we'd rather they didn't) due to more roosting places

How this wattle managed to become a flight hazard in Kunming is explained deeper in the paper. Prior to 2007, the airport was reclaimed land, once used for villages, farmland and planted forests. The latter included Black Wattle as a planted species and it's assumed there are extensive seed banks of the species in the soil. 

The climate around Kunming is very similar to southern Australia, which is why botanic gardens such as those of Sydney and Melbourne have sent expeditions to this area to collect suitable garden plants such as camellia species. 

Finally, plane movements themselves can move seeds around the airport land and then when new buildings or runaways are constructed, such activities break the dormancy of the seed. 

So all up this is another example of how by manipulating nature we can inadvertently cause ourselves a heap of problems. That's putting aside the local plants and animals that might be displaced. However with Fred Pearce's voice still reverberating in my head, I should note that at least 34 Chinese bird species live in and near the Black Wattle and may well thrive in its presence. That's if they stay clear of passing jet engines.

Images: all pictures other than at Kunming airport and the close of a Silver Wattle leaf (from near the Yarra River at Hawthorn) are from the Australian Garden, Cranbourne Gardens, part of the Royal Botanic Gardens Victoria.