Tuesday, 7 April 2015

A plant with a twist, nearly missed


It's so easy to miss a quirky flower or fruit in Melbourne's Royal Botanic Gardens. There is just too much going on. You have to always be on the look out for a fleck of colour here or a odd bauble way up there.

Back in early February I discovered this Corkscrew Tree on twitter. It was flowering beside a major path near the Canna Bed, but it wasn't until I tracked back from a tweet to MelbourneDaily that I realised it was in my own (work) backyard.

Nick V. posts occasional, and always well illustrated, posts on MelbourneDaily. His pictures are always great and he does his research. These are my pictures, with only a little more research!


Nick headed his story 'Pretty Deadly', which is a sure way to attract attention. Like lots of plants in the Apocynaceae (think Oleander) the Corkscrew Tree is poisonous in anything but extremely small quantities, and then sometimes medicinal. The PlantzAfrica website lists among its common names Poison Rope, Common Poison Rope and Forest Poison Rope.

I get the poison bit and thought perhaps the length of the unruly shoot heading out of this generally pruned plant (to the top right) might be an indication that its flexible branches are used for rope, albeit of a poisonous kind. In its natural habitat, in the forests of south-eastern Africa, I gather it is a scrambling climber.


My rope theory is supported by a Flowering Plants of Africa synopsis of the species but the genus name Strophanthus means 'twisted-rope flower', because the petals have a jaunty twist, so it may be that the term Rope in the common name references this too. In Australia we call it the Corkscrew Tree, again a reference to the flower. Or sometimes simply Corkscrew Flower.


The genus Strophanthus is widespread in Africa, with a handful of the 38 species in Asia. The various species pop up in herbals and healing websites, usually with strong warnings about the toxicity of the leaves and seeds.

Strophanthin, present in the seed of most species, is a little like digitalis in its action. It can stimulate muscles, like the heart, and it can kill when painted onto arrow tips (a single seed crushed and glued to the end of the arrowhead is enough to increase contractions then seize the prey's heart). Apparently, antitoxins from some species can be used to treat snake bites in the absence of specific anti-venom. Here in Australia though we have good access to anti-venom and it isn't a recommended method.

I was happy just to photograph and observe our species. The blood or red-paint splotch must surely attract the pollinating butterflies into the sexy middle of the flower. The white threads are appendages on the petals rather than the males parts of the flower (the anthers), which are nestled deep inside the flower with the female bits. (If you do tease a flower open you'll notice the real anthers are topped by lovely soft hair, looking very un-anther like.)

Once I'd got past the twisted, blushing flowers I noticed these large, pencil-shaped fruits. When they dry out, feathery seeds are released, carried away by the wind. Strophanthus speciosus was once separated out into its own (single species) genus called Christya because the tuft of hairs at the top of the seed is hardly stalked.


So just another plant, and another story. But I almost missed it!

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