Untangling the snake-haired gorgon

The spurges, Euphorbia, come in all shapes and sizes. Some look like cacti, some look like you might think something called a spurge would look with spoon-shaped grey leaves (bursting into heads of lime-coloured flowers), while others have dainty bouquets of red and orange blooms emerging from thorns or glossy green leaves. If you can imagine a plant form, there will be a spurge that does a damn good imitating of it.

The two I want to feature today are cactus-like, but with no barbs or prickles. Their stems mass together like the snaking hair of the mythical medusa, earning them the common name of Medusa Head Spurge. 

Vegetatively, the plant is a knobbly, green stem - which does all the photosynthetic work, soaking up the sun's energy to produce sugars for growth. You can see the spurge seems to half-heartedly produce (reddish tinged) leaves from time to time, but these soon drop.

As with many spurge flowers, their 'blooms' (and you can see a crowd of them at the top of the post, being inspected by a honey bee) seem to constructed from leftover flower parts from elsewhere in the plant kingdom. Plus some extra bits thrown in that don't always make sense (at least to a non-euphorbia-expert such as myself).

Now I said there are two spurges I wanted to feature today, both on the side of Guilfoyle's Volcano in Melbourne Gardens. On the plant label near one of them, and in our database, it says Euphorbia caput-medusae. That label sits next to the plant at the top of the post, with the bee.

This species name is one you might recall - or can at least search for - in my blog. I photographed and described what I thought was Euphorbia caput-medusae from our Southern Africa Collection on the other side of Melbourne Gardens.

What I seemed to miss last time is the 'flowers' illustrated above, with their predominantly white frills, are more the kind one should expect for this species. Rather than the radiating, slightly larger green to yellow fans with their little finger-like projections, as in this next picture (also from Guilfoyle's Volcano) and as illustrated in my previous post.

So what's going on? Are there two species? Was that one from the Southern Africa Collection (with the yellow-green fans) misidentified, and labelled, as Euphorbia caput-medusae?

It's only when you look more closely you see that the 'bracts' spreading out of the flowers from both plants are not that dissimilar. In one the fan part is larger and more prominent, in other its the white fringe. As I remarked last time, inside these bracts is a single female flower and six small male flowers. So the whole thing is a group of flowers gathered together, and in this case given the fancy name of cyathium. So not a single flower.

There are a few names circulating for these kind of spurges, such as Euphorbia woodii, Euphorbia flanaganii and the earliest described name (and hence to be used if any of these are considered to be the same thing), Euphorbia caput-medusae.

In fact there is a whole group, or section, within Euphorbia for plants of this general form and with flower clusters as described above. This group of species was for a time classified into a separate genus called Medusa, but that is now treated as a section within Euphorbia, still called Medusa.

I found it difficult to track down correct names for my two plants. The most alignment can be found on the World of Succulents page, with Euphorbia flanaganii for the yellow-green-bracted plant, and Euphorbia caput-medusae for the largely white-bracted one. Although there are references to Euphorbia flanaganii being for a time 'var. d' (presumably an unnamed variety) of Euphorbia caput-medusae.

I found myself tossed around on oceans of spurge taxonomy so decided to ask our curator of succulents, Bret Pritchard. He looked up the names we had been provided when we sourced them, and this one, with yellow-green bracts, is 'Euphorbia caput-medusae (small leaf)'.

And this one, with the white bracts, is 'Euphorbia caput-medusae (large leaf)'. Given the general absence of leaves, as I mentioned, there are interesting names. But there you go.

Both, I'll think you'll agree, are fascinating to look at, from a distance and close up. I suspect succulent enthusiasts, and perhaps my comrades in the Cactus and Succulent Society of Australia (which I enjoy very much being patron of, despite my obvious lack of expertise in these finer details), will correct my assumptions and conclusions here. For which I take full responsibility!