Friday, 29 June 2012

A botanical artist turns her attention to Celmisia

Celmisia is a mostly New Zealand genus of Asteraceae, with about 70 species.  Many of them are alpine, and each is beautiful in its own way.  Some are truly spectacular, but others are more subtle.  The late David Given devoted a lifetime of research to them, but even so, many taxonomic questions remain.
Celmisia spectabilis, Mt Ruapehu.
Now an emerging botanical artist, Eleanor Burton, has devoted several years to illustrating Celmisias with coloured pencils, and the results are truly impressive.  Eleanor's first exhibition is open right now in the foyer of the Department of Conservation's Head Office in Manners Street, Wellington: go and see it if you can.
Celmisia lindsayi at Nugget Point, Southland.
Celmisias are difficult subjects for the artist.  Like other composites, they're complex, with their hundreds of tiny florets.  What's more, they vary enormously in their leaf indumentum, which gives the leaves a silvery or greyish hue, which is difficult to illustrate.  Eleanor has captured the essence of these lovely plants in her drawings, in a way that invokes the appreciation one feels when seeing them in the wild.
Celmisia sessilifolia, Mt Robert.
This exhibition covers over a third of the genus, and I hope Eleanor will carry on to complete the set.  It would be a remarkable and valuable contribution to science.
Celmisia gracilenta, Kettlehole Tarn, Canterbury
I had the pleasure of being asked to say a few words at a function at the exhibition tonight.  The lighting didn't allow me to photograph any of the pictures, so I've illustrated this entry with my photos, but do go and see the pictures for yourself if you're nearby.  If you can't get to it, join me in hoping that Eleanor's pictures will be published one day.

Tuesday, 26 June 2012

Wednesday wildflower: she-oak

A planted grove of Casuarina cunninghamiana at Sunnynook Park, Auckland (Karly Garnock-Jones—photo)
I don't think there's such a thing as a he-oak, but there are she-oaks; they're a largely Australian plant family, Casuarinaceae, found also in Malesia (Malaysia, Indonesia, New Guinea) and many Pacific islands.  They're in the same order as the beeches, oaks, and chestnuts, but they don't look a lot like them.  The name she-oak is a reference to the hard figured oak-like timber; nothing else about the plant is oak-like.  Two species of Casuarina are naturalised in New Zealand, C. glauca and C. cunninghamiana.

They are flowering plants, but they look very like pines until you get close.  The branches are slender and have whorls of tiny leaves, so that each branchlet looks like a pine needle. Nearly all the photosynthesis probably takes place in these green slender grooved stems.

 The fruits are woody and arranged in clusters that look like little pine cones.  The female flower clusters even look a bit like young female pine cones in their first year.

The flowers of Casuarina are wind pollinated and unisexual, in clusters on separate male and female branches, or even on separate trees.  The fruits are small 1-seeded nutlets, but they're clustered together in woody pine-cone-like aggregations (the one below is about 10 mm diameter).
Casuarina cunninghamiana fruit cluster, after the nutlets have been dispersed.
Casuarina used to be in New Zealand as a native tree: here's a fossil fruit cluster from Bannockburn in Otago, in sediments of Miocene age.
It's one of a suite of Australian plants that flourished here when the climate was warmer, topography was flatter, and soils were infertile, rather like Australia today.  Mountain-building in the Pliocene and Pleistocene put an end to that version of New Zealand. Acacia, Eucalyptus, Casuarina, and many Proteaceae went extinct, and habitats were formed that suited the modern alpine flora.

Friday, 22 June 2012


Apocynaceae is a large tropical family that's not well-represented in New Zealand.  In the native flora we have just Parsonsia, so-called native jasmine, kaihua or akakaikiore.  In the naturalised flora there's oleander (Nerium oleander), periwinkle (Vinca spp.), and—because the family Asclepiadaceae is now included in Apocynaceae—swan plant (Gomphocarpus fruticosus) and a couple of others.  Plants of the family accumulate some nasty toxins, some of which are useful as drugs.

Like a lot of vines, Parsonsia leaves are very variable, sometimes with quite spectacularly different shapes occurring at adjacent nodes on a stem.  The leaves of young plants can be elongated with sinuous margins, elongated with an expanded tip, broad and elliptical, or even lobed at the base (Allan 1961 has an illustration), but the adult leaves are more consistently ovate.  Probably because of this variability, quite a few species have been described, but these were reduced to two by the time of Allan's Flora (Allan 1961), P. heterophylla and P. capsularis, to which P. praeruptis, a distinctive scrambling shrub from Surville Cliffs, Northland, was added recently (Heads & de Lange 1999).
Parsonsia heterophylla at Tunnel Gully, Hutt Valley.
The flowers are small, and resemble those of other Apocynaceae; they're like tiny frangipani flowers (Plumeria) and they do smell sweet.
Parsonsia heterophylla at Birdwood Reserve, Karori, Wellington.
Right now the fruits are ripening, although last year's empty ones are still on the vines.  These are long pods, each with a kind of double structure, so that when they open there are four valves produced, two broad and two narrow.
Parsonsia heterophylla fruits, line scale is 10 mm.
The seeds of Parsonsia are quite large, and wind dispersed.  Each has a coma (a botanical term for a tuft of hairs) that increases its surface area and allows it to float on the wind.
Parsonsia heterophylla seeds, line scale is 10 mm


Allan, H.H. 1961.  Flora of New Zealand Vol 1. Government Printer, Wellington
Heads, M.J.; de Lange, P.J. 1999. Parsonsia praeruptis (Apocynaceae): A new threatened, ultramafic endemic from North Cape, New Zealand.  New Zealand Journal of Botany 37: 1–6.
Sykes, W.R. 1988. Apocynaceae, in Webb, C.J.; Sykes, W.R.; Garnock-Jones, P.J. Flora of New Zealand Vol. 4.  DSIR, Christchurch.

Tuesday, 19 June 2012

Wednesday Wildflower: ivy-leaved toadflax

Ivy-leaved toadflax, Cymbalaria muralis, Wellington, New Zealand.
Toadflax is the English name for the genus Linaria and its relatives, plants related to snapdragons.  This little creeping one (sometimes also known as Kenilworth ivy) is common on cliffs and walls around Wellington and throughout New Zealand (the species epithet muralis refers to its preference for walls).
Cymbalaria muralis, Kelburn, Wellington, New Zealand.  A, flowers, the one at far right is being gently squeezed with forceps to open its throat; B, leaves, the large one is from a shaded site; C, fruits on their elongated stalks.
 Its leaves are bigger in the shade, and slightly fleshy.  It does well in full sun, although even the sunniest cliffs and walls are usually shaded in either the mornings or afternoons.
Cymbalaria muralis, Karori, Wellington.
There are some interesting features to these little purple and yellow flowers.

First the entrance to the flower is closed by a palate (the two yellow knobs in the flowers above), which must be forced open by the pollinator (usually a bee).  You can play snapdragons with these by gently squeezing the flower tube from the sides, but they're not as spectacular as the true snapdragon, Antirrhinum majus.  They are both classified in the same family, Plantaginaceae (along with a bunch of plants with more open flowers, like Veronica and Plantago).

Secondly, behind the flower is a long nectar spur, which holds the reward the bee is seeking.  The bee needs a long-tongue to get the nectar.  New Zealand has no native long-tongued bees, but introduced bees can pollinate toadflax.  Interestingly, we have no native flowers with closed throats and nectar spurs.

Thirdly, the flowers are held above the leaves, but after they're pollinated the flower stalk curves downwards below the leaves and elongates, holding the developing fruit close to the soil.  By the simple expedient of growing the stalk (probably by elongating cells, especially on one side, to generate a curve) the optimum positions for both pollination and seed dispersal can be achieved.

Ivy-leaved toadflax is native to Southern Europe, and probably came to New Zealand as a cultivated plant, like so many species that are now wild.  It was first reported as naturalized here in 1904 (Sykes 1988). Although it's now classified in the family Plantaginaceae, but for many years it and many of our other Plantaginaceae were considered to be part of the Scrophulariaceae.


Sykes, W.R. 1988.  Scrophulariaceae, in Webb, C.J.; Sykes, W.R.; Garnock-Jones, P.J. Flora of New Zealand Vol. 4.  DSIR, Christchurch.

Saturday, 16 June 2012

North Shore beaches

I'm in Auckland for the week and weekend.  It always feels a bit different from the rest of New Zealand.
The low cone of Rangitoto Island, Auckland's youngest of many volcanoes, dominates the harbour entrance.
I was hoping for a botanical walk today along some of the beaches on Auckland's North Shore, but although it's a nice place to walk, the plant life we encountered was uninspiring.  The place is just too kempt.  The scenery was pretty though:
The beach at Campbell's Bay
Some of the interesting plants were in private gardens, like this pukanui, Meryta sinclairii.  It's native to the Three Kings Islands, in the far north of New Zealand, but often cultivated.

These flowers were being mobbed by introduced honey bees.

The cliffs are fringed with pōhutukawa (Metrosideros excelsa), arguably our most beautiful flowering tree (family Myrtaceae).
Metrosideros excelsa, near Campbell's Bay (Karly Garnock-Jones, photo)
On the cliffs an introduced African daisy Osteospermum ecklonis was occasionally naturalised.

We followed the cliff tops for a way to avoid the rising tide, and stopped for lunch at this view of the Hauraki Gulf:

Lunch was the best part: cold roast beef sandwiches, on Turkish wholemeal & walnut bread, Zerrin Gunaydin's delicious recipe.  You should check out her foodie blog.

It was a nice day out, not very botanical, but a very pleasant walk.  It got a bit cold around the middle of the day, but then the sun came out again.

Tuesday, 12 June 2012

Wednesday Wildflower: tree lucerne

When we lived in Okuti Valley on Banks Peninsula, there was a tree lucerne right outside the back door, and there were nearly always a couple of kererū (New Zealand wood pigeons) in it, feeding on the young shoots.  In spring they'd move to the poplar shelter belt (we counted 35 there one day) and in summer they'd be feeding on fruit, including the neighbor's plums.

Tree lucerne is a common woody weed in New Zealand, but it's one of those weeds that's not really much of a problem.  It was deliberately introduced (sometime before 1919) as a hedging plant and as livestock food, hence the New Zealand name, which is a reference to lucerne or alfalfa (Medicago sativa).  It comes from the Canary Islands, where it's known as tagasaste, a name which is sometimes also used in New Zealand. Now tree lucerne is naturalized pretty much throughout the country.  Its value as a fodder plant is also reflected in its value as a food for kererū.
Tree lucerne, Chamecytisus palmensis. A, a cluster of flowers; B, flowers, seen from the side and from beneath; C, seed pods developing; D, leaves: upper surface on left; E, seeds.
The flowers are typical of the legume subfamily Papilionoideae.  They have 5 petals: a large standard or flag petal, clearly seen in B above; opposite that is a keel that's formed from two petals joined together; and alongside the keel is a wing petal on each side.  The standard overlaps the wings and the wings overlap the keel.  The pale structures at the stalk ends of the seeds are strophioles; their function is associated with water uptake by the germinating seeds.

Tree lucerne, Chamaecytisus palmensis, near Northland Tunnel, Wellington, New Zealand.
Here in Wellington tree lucerne is common on roadside banks and cliffs, and can form a trunk a few metres tall and 150 mm diameter.  The white flowers form during winter and are a source of nectar for bees.

Like gorse and other legumes, it's a nitrogen-fixer, or at least it harbours bacteria that are nitrogen-fixers.  That's part of its value as a livestock food, and also might give it a role in eco-restoration, as a nurse crop for native forest regeneration.  If kererū are attracted to the leaves, they might bring seeds of native plants to regenerate under the shelter of the tree lucerne.

This is a plant with so many virtues, it's perhaps unkind and misleading to call it a weed, and you'll note I've renamed the series "Wednesday Wildflower".

Thursday, 7 June 2012

Why are botanists so ...

A commenter on Pharyngula wanted to know what people thought of Australians, so did a Google search on "Why are Australians so". I did it for botanists. Here's what I found.
  • "Why are botanists so much more successful in understanding their discipline than we lepidopterists? 
  • "Why are botanists so much nicer to get along with than mathematicians?
  • "Why are botanists so interested in Phylloglossum?
  • "Why are botanists so cute?"
That's the sum total for the whole internet, so I guess most people don't have any opinion about botanists, or else they know why we're all the other things we are.  I'm happy with "nicer to get along with", and "cute".

Tuesday, 5 June 2012

Wednesday weed: velvety nightshade.

This one's velvety nightshade, Solanum chenopodioides.  Both its names are descriptive, because the leaves feel velvety due to fine dense hairs all over them and they are similar in shape and colour to Chenopodium album, hence chenopodioides.
Solanum chenopodioides.  A, leaves, underside on left; B, flowers; C, a flower cluster; D, leaf edges and surfaces, lower on left; E, stem; F, a fruit cluster (unripe).
Velvety nightshade and black nightshade, S. nigrum, are the two commonest nightshades around Wellington, often growing together in waste land and roadsides.  Velvety nightshade is a South American plant, like so many of the genus, whereas black nightshade is from Eurasia.

Solanum and its family, Solanaceae, have a lot of poisonous plants.  Many contain solanine and chaconine, which are inhibitors of the chemical reaction that stops a nerve impulse from endlessly firing along the nerve.  When that reaction is blocked, the nerve doesn't switch off, with disastrous effects.  These toxins are advantageous to the plant, because they can inhibit the activities of insects and other predators.  Potatoes (Solanum tuberosum) may have small amounts of solanine and chaconine, but not enough to affect us because our livers break down that small amount pretty effectively.

Crops like potatoes have been selected over centuries of farming for reduced amounts of the natural pesticides that many plants have.  Much of early crop selection was inadvertent, with growers cultivating next year's crop from the survivors of this year's.  (And of course if the crops contained some toxins, it was only the surviving growers—those who had eaten less-toxic strains—that were around to plant the crop again).  So the crops became less toxic, but often retained some toxicity that prevented them being lost to pests.

Crops' wild relatives sometimes still contain toxic amounts of these natural and organic pesticides. So here's a bit of admittedly rank speculation: I wonder if pollen from wild relatives could ever contaminate a crop, making some plants in the next generation more toxic (i.e., naturally pest resistant).  Then, hybrid plants with higher levels of natural toxins should compete better with the non-hybrid plants, especially if pesticide sprays weren't being used, as on organic farms.  Organic growers might even prefer to grow them for their higher natural resistance to pests, and inadvertently select strains that are more toxic to humans.  I emphasize I have no evidence that this happens, but I wonder if anyone's looked?  And I'm certainly not suggesting these wild nightshades hybridize with potatoes; Solanum is a big genus and most species aren't closely related or genetically similar enough for hybrids to form.