Tuesday, 30 June 2015

Milkweed munching mariposa in Buenos Aires

This is a milkwort, host plant of the famous mariposa butterfly. At Mariposa Grove in California last year (viewing the giant sequoias, Sequiadendron giganteum), Lynda and I were musing on the link between that location name and the butterfly. It turns out the Grove was named after the County which was named after the Creek which was named after the butterflies - the mariposas - that gather in this vicinity each year in May. We call the same butterflies Monarch or Wanderer Butterflies.

In Buenos Aires earlier this year, I encountered the word mariposa again, this time in Jardín Botánico Carlos Thays, that city's botanic garden. This time it was the real thing. The butterflies were living part of their life cycle in a specially planted, and spectacularly successful (at least on the day I was there), butterfly garden.

Most butterfly gardens are inside glasshouses, to keep in the butterflies and perhaps stop the sometimes weedy butterfly attracting plants from escaping. In this case it was possible to grow enough butterfly attracting plants - e.g. lantana - outdoors, and to attract enough wild butterflies.

For the whole time I was in the Buenos Aires butterfly garden - mid-morning on a sunny day after early rain - there enough flitter-flutter to keep the smallest child or easily-amused adult entertained. I even saw a hummingbird, briefly.

The star of the show was the Southern Monarch Butterfly (Danaus erippus, or sometimes Danaus plexippus erippus), present in wing and grub. I gather this is a different species (or sometimes subspecies) to the one we have in Australia, Danaus plexippus, which is also the Monarch Butterfly that flies from Mexico to northern USA each year. That species only arrived in Australia in the 1870s, perhaps (incidentally) by boat, but is now well established  in the east and south of the country (and beautifully photographed for Sydney's Royal Botanic Garden Facebook page by Jaime Plaza).

It seems that the southern and northern (American) species both lay eggs under the leaf of the Tropical Milkweed, Asclepias curassavica, but the Southern Monarch Butterfly also favours other species in genus and few others. Here the caterpillar of the Southern Monarch Butterfly is happily nibbling on Tropical Milkweed in the botanic garden of Buenos Aires.

In both species, the eggs hatch to produce a black-and-yellow striped caterpillar that over a fortnight munches its way through as much milkweed as it can, bulking up to 2000 times its original size (along the way shedding its skin five times). After pupating the familiar orange-and-black butterflies emerge to either fly about locally for 2-6 weeks (then dies) or, for specially bred kinds, to migrate up to 3000 kilometres or more (drinking nectar along the way and taking advantage of warm air currents) and live for eight months.

And migrating is something they are famous for. Every spring marioposas arrive in northern USA from overwintering in Mexico and thereabouts. The breeding butterflies I saw in early April in Buenos Aires were presumably short-lived ones enjoying the warmth of the (Southern Hemisphere) autumn. The migratory butterflies are sterile it seems, but for the Southern Monarch Butterfly there is still plenty to learn. 

But back to more or less familiar plant territory. Tropical Milkweed is in the family Apocynaceae, well known for including plants with often toxic milky sap. In this species the toxins would kill many animals but not this caterpillar. More than that, the toxins accumulate in the caterpillar and then later the butterfly, making them both toxic to predators.

The fluttering stage feeds on nectar, from the milkweed but also many other flowers. In this case it's a local lantana. Well I say 'local'. It's been planted obviously but I think Lantana camara does naturally around Buenos Aires. As to the origins of the milkweed and the mariposa, I'm less sure.

Tuesday, 23 June 2015

Covert surveillance reveals China Doll

Over summer my wife Lynda and I would sit in the small courtyard at the back of our home and soak up the evening warmth, making up for two years of deprivation in London (we experienced particularly miserable summers there) and winding down from our days of teaching and botanising, respectively.

We mourned the removal of a jacaranda from the property behind us (revealing far more of the neighbouring flats that we wished to see) and surveyed the landscape around us for more optimistic plant futures. One of these was a 10 metre high tree in our next door neighbour's back yard. It had dramatically elongated white flowers, a bit like a Trumpet Flower (Brugmansia) or Gardenia thunbergia if you know that one.

The flowers were just too far away to see the floral detail but it looked like the leaves of the tree were finely branched - pinnate. Over the weeks the flowers came and went, but more kept coming, and eventually long narrow seed pods were extruded from the spent blooms.

Armed with my telephoto lens I took these pictures one evening late in the season (mid-February) but as luck would have it there were no open flowers. I could see, and photograph, some buds so there were more to come. We guessed they might open at night given they were big and white, more suited to moths (maybe the famous hawk moths with their long 'tongues'?) and bats, rather than daytime fauna, and sure enough by the next morning there were some new flowers to photograph.

They were drooped and ragged by mid-afternoon of what turned out to be a 35 degree Celsius day but with more buds for tomorrow. It seemed to flower for many weeks.

Guessing at the family Bignoniaceae based on the pod I eventually tracked the species down to Radermachera sinica, a species that we have planted frequently in our southern China collection at the Royal Botanic Gardens (as well as near the lakeside toilets along from what is called the Taxodium Lawn). It grows naturally in southern and eastern Asia.

In Zambesia (the source of the on-line key I used to identify the genus and species) the China Doll Plant, as it is also known, is widely planted for its 'showy flowers'. Worldwide this species is perhaps better known as an indoor foliage plant, trading under the name of China Doll. In Melbourne it will grow outdoors in a sheltered spot, like my neighbour's backyard. (You may also find a compact cultivar of a related species from Yunnan, in southern China, called 'Summerscent', which has been hailed as a rival to Murraya.)

There are 17 accepted species of Radermachera, a genus named after Jacob C.M. Radermacher, an 18th century Dutchman who lived in Java. We have two species in the Royal Botanic Gardens, one specimen of Radermachera gigantea (with mauve flowers) in the fern gully and, as I know now, a southern China collection riddled with Radermachera sinica (with its white to soft yellow flowers).

So that's what it looked like in mid-February. Now, in mid-June, there only twisted seed pods, mostly open and with seeds dispersed. Here is a close up taken last weekend, on a day reminiscent of a summer's day in London. It's the last of my covert photography across the fence ... unless of course I spy something else botanically interesting.

Tuesday, 16 June 2015

Chilean mock holly depends on edible dormouse

There were few plants in flower when we trekked up through Nothofagus (southern beech) forests to see the Monkey Puzzle Trees in southern Chile. Our tally for the Huerquehue National Park near Pucon included one flowering Canelo or Winter's Bark (Drimys winteri) - yes one, plant - and a single flower on a 'gesneriad' called Sarmieta repens - yes one, flower.

There were two obvious exceptions to this flowerless landscape. One was Fuchsia magellanica, the fuchsia we all grew up with in our home gardens but here growing in its natural habitat shaded by southern beech. The other was Desfontainia spinosa.

Consistent with its charming genus name (after French botanist René Louiche Desfontaines) it's a pretty little thing, particularly in flower. If I tell you it's in the Columelliaceae, or sometimes its own family, the Desfontainiaceae, I'm sure you are hardly better informed. Columellia is another South American genus and both genera have only a couple of species. Perhaps its previous allegiance to the Loganiaceae helps?

Anyway, let's stick with the species I now know. The common name Chilean Holly tells you a bit more about what it looks like: it has leaves which are prickly on the edges. However these leaves emerge from the stem in pairs, rather than alternating from one side to the other as happens in true Holly (Ilex).

But the flower grabbed my attention in April this year and its these that grace this post, all tantalisingly just out of focus due to the low light levels... In addition to botanists, the flowers attract Green-backed Firecrowns, a local hummingbird. (I didn't see any hummingbirds here but was excited to see one visiting a Chilean Bell Flower back at our hotel.)

We didn't see any fruits but it seems the seed is only distributed via the faeces of an animal charmingly described by the World Heritage Encyclopedia as 'an edible dormouse-like marsupial'. The Dromiciops gliroides is commonly called Chumaihuén or in Spanish, Monito del Monte, which translates as the ' little monkey of the mountain'. Apparently it eats the berries of lots of local plants and by defecating them into new places, helps them get about.

In the fourth volume of Roger Spencer's Horticultural Flora of of South-eastern Australia he says this species is 'the source of a yellow dye and its leaves are used for a medicinal tea'. I'd be a little wary of the medicinal uses given the psychedelic language and warnings in apparently ethnobotanical posts such as this one from  Botanical Guides . And the preponderance of the word 'shaman' in this and many other posts on the species also suggests this is a plant to avoid.

Roger describes it as 'occasionally grown'. We used to have a couple in Melbourne's Royal Botanic Gardens but not anymore, which could be described as occasional. Apparently growth is slow in cultivation - taking up to 20 years to reach the grand height of 2.5 metres - but I did notice it was recommended warmly for mildly cool climates, like Scotland, as long as you it was grown against a wall.

Oh, and it doesn't like acidic soils but enjoys a bit of waterlogging. So they say.

Tuesday, 9 June 2015

Grow Franklinia and give a plant without a home, a home

I was asked the other day by someone moving from Mount Macedon to North Fitzroy whether they could grow Franklinia alatamaha in their new garden. An unusual question about an unusual species. This is not the first tree you'd think about planting.

The questioner was a writer who doesn't really write about gardens but clearly does have an interest in them. So I tried to help by saying, probably not. At Melbourne's Royal Botanic Gardens we have one specimen in our nursery (donated to us two years ago by Peter Teese of Yamina Rare Plants) but none growing in the main collection.

While you can find this species in specialist nurseries around the world, it's extinct in the wild. There is no last chance to see what is sometimes called the Franklin Tree, unless you visit a garden, and not yet Melbourne's Royal Botanic one.

The story of Franklinia is summarised well on the Missouri Botanical Garden website, with more detail provided by Lucy Rowland in an article published in Terrain.org, It starts with King George III of England appointing the Quaker farmer John Bartram as his Royal Botanist for North America in 1765.

In his first year as Royal Botanist, Bartram and his son William found an attractive small tree on the banks of the Altamaha River in Georgia. The trees grew throughout a hectare or so of river frontage but nowhere else in Georgia, in North America or, at that time, in the world (perhaps the universe, but harder to confirm).

Son William returned to Georgia in 1773 to collect seed which he successfully germinated and grew in his garden in Philadelphia. It turned out to be an attractive specimen and became increasingly popular in North American and European gardens.  It also turned out to be a new genus.

In 1785, William Bartram's cousin, Humphry Marshall, gave the plant its botanical (and hence common) name, honouring the 18th century polymath and friend of the Bartram family, Benjamin Franklin. The species epithet is an odd spelling of the river name.

Franklinia was, and continues to be, classified in the plant family Theaceae, along with Camellia (the source of tea and of lots of pretty garden plants), and Gordonia and Stewartia (both with flowers and leaves a bit like Franklinia). There is only one species of Franklinia although you do sometimes see the Fried Egg Plant, Gordonia axillaris, and other species of Gordonia, called Franklinia. That classification isn't generally accepted.

Franklin's Tree looks quite a bit like these other genera but is always deciduous (like Stewartia), giving it the lovely autumnal colour in the image above. Unlike Stewartia, it has flowers without any stalk (see the stamp at the top) and a woody fruit that splits alternately from the top, then the bottom (as you can see here...).

Unfortunately, in the tail end of the eighteenth century most of the land around Altamaha River was cleared for cotton farming. The cotton also brought with it pathogens that may have spread into the fragments of remaining native vegetation killing plants like the Franklinia. Climate change and floods have been blamed too, but in any case the tree was extinct in its natural habitat by 1803.

Which is why all plants you see alive today are sourced from seed gathered from Bartram's tree grown in Philadelphia or perhaps from other seed collected in 1773. The result is a consistently pretty garden plant with little genetic variation.

You don't see it often in Australia. When I was Director of Royal Botanic Gardens and Domain Trust in Sydney I tried to find a specimen in the collection there, just out of curiosity. I was unsuccessful although it was listed on the census as growing in the 'Rare and Threatened Bed', one of the rectangular formal gardens near to the National Herbarium of New South Wales building. Rare and threatened I guess, if that's a compromise between extinct in the wild and uncommon in cultivation.

Lucy Rowland says Franklin's Tree is easy enough to propagate from cuttings or seed but difficult to transplant, susceptible to root rot and 'not...particularly vigorous'. It needs rich, well-drained, acid soil and plenty of water, just like it had by the riverside. It tolerates cold better than severe heat it seems.

So it should perhaps be more widely grown in southern Australia, albeit in cooler mountain districts. That said, on reflection, my friend lately of Mount Macedon and recently of North Fitzroy should give it a try. Such a fascinating pedigree deserves special horticultural effort.

Images: The stamp at the top was issued in 1999 and the image has been copied from eBay, but you can find another in the U.S. Stamp Gallery. The fruit is from a fact sheet on the Virginia Tech website. The other pictures are of the specimen in the Royal Botanic Gardens Melbourne's nursery in late March.

Tuesday, 2 June 2015

It's holly mate

Yerba mate, or simply mate, is a gritty suspension of plant fragments sucked through a hot metal straw called a bombilla. In much of South America, and also parts of the Middle East where it was more recently introduced, you can get your daily caffeine fix from a cup of mate.

The cup was, and sometimes still is, a hollowed out gourd (something from the melon plant family) but these days it can be anything from wood, to glass to plastic.

Typically you share the brew with friends, much like you would a block of chocolate or perhaps a bong. It's not uncommon to see young people in Buenos Aires carrying their mate cup and bombilla in one hand, and a thermos of hot water in the other.

The plant is a local species of holly, Ilex paraguariensis, sometimes but not authentically mixed with other spices and herbs. Originally the plant was collected from the wild by native South Americans, but Jesuits started to culivate Ilex paraguariensis to meet demand and to produce a higher quality product.

The plant has very particular growing requirements, requiring a warm, humid climate and acidic soil. But it can be coaxed into growing outside its comfort zone. The botanic garden in Buenos Aires recently planted a small crop for display and to get healthy and productive trees they excavated a metre or so of soil, replacing it with loam from the plant's natural habitat.

You start with a lot of plant material stuffed into the small cup, adding boiling water. Then suck, swallow and share. After a few slurps you need to add more water and that's when you pass the cup to your mate...

Although confusing in Australia where 'drinking mate' refers to the blokes and sheilas in your shout, it's mate rather than maté according to Encyclopædia BritannicaMaté is Spanish for 'I killed' and the accent is only added by English-speakers to help with pronunciation, and perhaps avoid confusion in the pub.

Plenty of benefits are ascribed to the drink, but also warnings about prolonged use. The Natural History Museum in London describes it as a 'nutritious beverage' and some of the alkaloids stimulate our nervous systems in the same way as coffee and chocolate. The links with cancer are associated with the piping hot bombilla, with which I certainly managed to burn my lips and mouth.

The specially dried leaves (and little twigs) are rehydrated only briefly with hot water for the first dose. It's non-alcoholic but packed full of caffeine and tannins. To me it tastes much like black or green tea, Camellia sinensis (from Asia) but more so.

I enjoyed it about as much as tea and will stick with my Ethiopian plant of choice, Coffea arabica.

Tuesday, 26 May 2015

Megafruit pining for absent megafauna

From a distance this 25 metre high tree looks like a flowering gum of some kind, a bloodwood (Corymbia) perhaps. The large leaves and, in February, the clusters of pink flowers are quite misleading.

Sort of. It's the right family, Myrtaceae, but wrong genus. This is a Lilly Pilly, Syzygium moorei. The fruits, when they form in March, give it all away. As does the location of the flowers and the fruits, clustered around the stems and branches. In a flowering gum they would be at the ends of branches.

This type of flowering and fruiting is called cauliflory, which I've mentioned before in passing. Why plants do this probably depends on the particular species and its pollinators, but it happens most commonly in tropical or subtropical rainforests, the natural habitat of our species.

Flowers packed around the branches are usually more firmly attached and less likely to be removed by a large pollinating creature, such as a bat or mammal. In this mature tree all the flowers are well above the grazing height of a ground-dwelling animal, but well place for climbers and creepers.

Syzygium moorei is called by local Aboriginal people the Durobby or Coolamon, Europeans have named it Rose Apple (a name applied to a few lilly pillies) or Watermelon Tree. The last name gives you a hint about one of its distinctive features - big fruits. Although not that (watermelon-sized) big. These fruits still had a little growing to do when I photographed them in in early May, but they are close to their final size of 3-5 centimetres in diameter, and their final colour - white.

The relative bigness of the fruits got scientists thinking about what might have eaten then before humans settled in Australia over 60,000 years ago.

Lui Weber speculates on this in an article in Wildlife Australia about plants not doing so well after the demise of Australia's megafauna. He suggests that Durobby is a 'rainforest tree with big fruits and a tiny subtropical distribution (Richmond River to Mudgeeraba area), consistent with it being a plant that depended on now-extinct cassowaries for dispersal'.

So where are the cassowaries in Australia? They have a fragmented distribution north of Townsville up into Cape York. These days they certainly don't find there way down to the Gold Coast in southern Queensland, the north-east corner of New South Wales,  

Weber is worried about the future of Durobby and other rainforest species in Australia. In the absence of a big animal to eat the fruits and disperse the seed (out their rear...) the advantage of producing relatively few, larger seeds becomes a liability. All that energy and risk without a suitable animal distributor. Relatives and neighbours of the species produce small seeds and are still well served by the local animals. 

Where did the 'megafauna' go? In the same issue of Wildlife Australia, fellow Australian ecologist Chris Johnson concludes that while the drying climate may have hastened the decline of rainforest species, many big herbivores found it a positive change, giving them opportunities to evolve and spread into new habitats. Overall it was most likely hunting by humans that sent the megafauna to extinction. This over time, may send some of our megaflora the same way.

In Africa, a reduction in the number of elephants due to habitat destruction and hunting is having a similar impact on large-seeded rainforest plants, which are now finding it difficult to regenerate and disperse. In Australia, the White Bark (Endiandra compressa) is distributed widely throughout the remaining tropical rainforest up north where the cassowaries distribute its seed, while in the south it clings to the side of streams where it probably relies on 'water, rodents and gravity'. 

There are fossils leg bones of a cassowary species in southern Queensland, a dwarf species like that found in New Guinea today. This may have been our plant's megafaunal companion. Weber suggests that 'one way to help [plants like the Durobby] would be to reintroduce cassowaries to southern Queensland and northern New South Wales'. The next decision would be whether it's the larger northern Queensland species or its smaller relative in New Guinea.

A dwarf or regular-sized cassowary couldn't reach the fruits on our Durobby so presumably they fall to the ground first. In the Royal Botanic Gardens we have no plans to introduce Cassowary, or for that matter elephants.

Tuesday, 19 May 2015

Wine palm a very ugly 'tree'

Palmas de Ocoa, La Campana National Park is about a one hour drive out of Santiago, Chile, and famous mostly for its stands of Chilean Wine Palm, Jubaea chilensis. This species, the only one in its genus alive today, is restricted to only a few populations in central Chile. It grows further south than any other palm in South America.

Mostly it occurs on steep slopes of high mountains but in the La Campana National Park is grows in an accessible valley which Lynda and I visited under the guidance of Estela Davis and Catherine Kenrick from the Chigual Botanic Garden in Santiago.

The park also supports lots of other species restricted to this region. Our visit in autumn meant we were not destracted by many flowers but the local cactus Quisco (Echinoposis chiloensis) supports a leafless mistletoe, Tristerix aphyllus, which was in vivid red flower.

And there were the two species of large-flowering bromeliad, Puya beteroniana (with blue-green flowers) and Puya chilensis (with yellow flowers). Both had dry brown floral remnants when we visited in April.

But most importantly this is where the Chilean Wine Palm grows most abundantly today after its range has been severely reduced due to land clearing and fire, its seed traded as currency and many of the plants harvested (cut, then placed on their side to drain) for fermenting of the sap. Here, reaching up to 30 m, it towers impressively above nearby vegetation. Like the Monkey Puzzle Tree further south, it is an ‘architectural’ plant, described by Estela as like a column from a Greek or Roman temple.

Not the most elegant of columns perhaps. Charles Darwin dismissed it as 'a very ugly tree', despite it not technically being a tree but more accurately a giant grass or lily. The trunk starts out nice enough but narrows, unattractively to some, after 60 to 70 years. Noone is quite sure why this happens but one of the popular theories is that the change occurs after it first flowers, which takes about this long. It's a slow grower, and this is what an avenue of Chilean Wine Palms (in Jardín Mapulemu, in Santiago) looks like after a decade or two.

When young it can be easily mistaken for the more commonly planted, and somewhat weedy, palm from the Canary Islands - Phoenix canariensis. The difference lies with the crease in the leaflets. They fold downwards in the Chilean Wine Palm and upwards in the Canary Island Palm.

There is plenty of seed produced in the wild, and a nursery nearby within the private park 'Cocalan' was propagating large numbers for horticulture. Until recently, when it had to be removed to allow for a £35 million restoration of the Temperate House, London's Kew Gardens was home to a specimen planted as a seed in 1846 and arguably the tallest plant in a glasshouse. Here it is on its last day, just over a year ago, with only a few other palms for company.

In RBG Melbourne we have a number of specimens perhaps a 100 or more years old, growing outside. A particularly statuesque specimen (hardly narrowed at its top, interesting given its age) was planted on the lawn behind the Herbarium in 1904 by the Government Astronomer, Robert Ellery.

Tuesday, 12 May 2015

Strange staminal swellings on Gold Medallion Tree

The Gold Medallion Tree, Cassia leptophylla, has large clusters of (appropriately enough) big, yellow flowers. These medallions were particularly dramatic in January this year, weighing down a specimen just opposite the Rose Pavillion in Melbourne's Royal Botanic Garden.

In California the Gold Medallion Tree is celebrated as one of the few 'tropical trees' that will flourish in LA and beyond: "Although it shares the large, showy flowers and tropical-looking foliage of its cousins, gold medallion tree is much hardier to frost, dry heat, and drought than the other two (Cassia fistula and Cassia nealiae) — and that’s what makes it special in California". Sounds like a good plant for gardens in southern Australia.

Take another look at that flower at the top of the post. What caught my eye - or to be fair Neville Walsh's then mine - was the capsule-shaped swelling on the three larger filaments (the stalks of the male part of the flower, the stamen, terminating in the pollen-bearing anther). It's true we were attracted by the in-your-face flowers to start with, but up close these golden tabules are rather odd.

Golden Medallion Tree is the only native American species with this kind of weird swelling on the filaments, although Cassia ferruginea, also from Brazil, has filaments with a gradually flattened expansion towards the end. Elsewhere, the pink- or purple-flowered Cassia javanica from central and southern Asia has a very similar swelling but this is thought to have arisen independently (that is, through what is called parallel evolution - similar pressures, perhaps, producing similar looking adaptations).

But why produce these swellings in the first place? Dunno. They don't seem to produce anything like nectar or act in an obvious way to make the flower more attractive to pollinating insect or bird. Perhaps they give a foothold to any visitor trying to get to the more lucrative female bits of the flower?

Gold Medallion Tree is said to have a 'massive four-angled pod', up to 70 cm long, but I gather they are rarely formed. There are definitely none on this particular tree, now four months after flowering. The leaves are still there, though, attractive but less mysterious.

Although...why so many (a dozen or so) pairs of 'leaflets', and why does the leaf end in a pair rather than a single leaflet? The terminal pair makes the botanical description of the leaf just a little simpler, being paripinnate (a equal number of pinnules or leaflets) rather than imparipinnate (an odd number of pinnules and leaflets, implying a single terminal one).

The Gleditsia japonica next to it, also paripinnate, has lost all its leaves. In full leaf they are difficult to tell apart (in the picture below Cassia, in flower, is on the left, Gleditsia on the right). In fact in it was a question of identity that drew Neville Walsh to the tree in January. Someone had commented on these flowers being rather odd for a Gleditsia, which tend to have small greenish flowers (as in the Honey Locust), thinking a branch of one was the other. The Gleditsia has the last laugh, though, with a number of fruit pods evident yesterday.

Note: There was supplementary question once the identity of the plant was sorted, as to whether this tree, a Cassia, might be an alternative source of cinnamon. The answer was no. Neville Walsh explained that cassia bark, sometimes used as a substitute for the bark of Cinnamomum verum ('true' cinnamon) and reputedly able to hold its flavour better during cooking (although reputedly more bitter and of inferior flavour), comes from Cinnamomum cassia

And for some better pictures of the Gold Medallion Tree in Melbourne's Royal Botanic Gardens, see the January 2013 blog post by Nick V. at Melbourne Fresh Daily.