I've written about euphorbias that look like cacti, and some that don't. I've also mentioned before that if a flower looks odd and you can't work out what family it's in, then it's probably a member of the Euphorbiaceae. You could add that if the flower is nothing to write home about, ditto.
This one in Castlemaine's Botanical Gardens is a common bedding plant, Euphorbia rigida. It will be part of adapting the botanic garden's plant collection and landscape to a drying climate, something that no doubt would have been useful right from the inception of the garden more than 150 years ago.
Still, things are likely to get tougher for plants in south-eastern Australia as we blaze our way into the twenty-first century. At Melbourne Gardens, we have included this species in our low-water-use garden. This next picture is from that garden, the rest in the post from Castlemaine.
Perhaps more interestingly, this species, like all euphorbs, contains a white milky substance. You may remember Euphorbia peplus, the source of a cure for skin cancer. Often the exudate is both poisonous and irritating to the skin, but it also has become another potential source of biofuel.
Euophorbia rigida is one of the species commonly reported in biofuel trials. It's popular in places like Turkey because it is widespread and, as we know, able to grow with little water or attention. The Gopher Spurge, as it is sometimes called, grows naturally around the Mediterranean and through the Middle East.
So this plant is an interesting mix of a good garden substitute for drier times and a possible source of energy to replace damaging fossil fuels. The perfect climate change plant? You just know the down side is that it will be weedy. Well, not in Victoria, at least yet. There are only two records in Australia's Virtual Herbarium, both from the Swanston Street Mall in central Melbourne collected 20 years ago, and none in the Atlas of Living Australia.
I notice there are reports of Euphorbia rigida escaping into native vegetation in California, but at least in 2012 it was not considered naturalised - i.e. persisting and reproducing in nature. Do keep an eye on it and definitely don't dump it into bushland (which should go without saying of course) and for now, enjoy.