Perhaps this odd plant would have been an appropriate species to feature for April Fool’s Day, because it is full of trickery.
Given it is held in a collection at the University of Alberta Botanic Garden, a common misidentification of this small succulent is to presume it is an indigenous cactus, but it is not. In appearance, it seems as if someone had left a baseball on the sand in our greenhouse’s succulent display. But then the baseball flowered! Even the flowers were a trick, though, because species of Euphorbia produce specialized bodies called cyathia or “false flowers” (the true flowers are hidden well within these structures). The trick to nature was that this flowering happened in March (in the greenhouse) where there were no insects for pollination. Oh yes, better get two of them if you want to produce offspring because the mischievous Euphorbia obesa is dioecious, with each plant sporting either male or female flowers.
The globular form represents a low surface-to-volume ratio, thus holding moisture in the succulent plant body and therefore aiding the plant’s ability to weather extended droughts. Sinisterly, that moisture is unavailable to us as humans because the milky sap, called latex, is toxic. This toxicity is speculated to have evolved as an anti-herbivore defense mechanism against the abundant native grazers of the species’ South Africa origins. Ironically, many of those grazers are now extirpated or extinct. Toxic for nothing. Is anything as it seems with Euphorbia obesa?
This euphorb is one of many occurring in the harsh desert conditions of South Africa’s coastal Cape Province. The wide diversity of isolated habitats provided abundant microclimates for species radiation over the Great Karoo and its many subregions over the last 100 million years. Adjacent to, but distinct from, the Euphorbia obesa range is the Fynbos region’s 8000 plant species occurring in a belt along the coast; of those plants, 6000 are endemics, making it more speciose than any South American rainforest. Many plants of the Karoo and Fynbos are cultivated in botanical collections where their active conservation contributes to maintaining genetic lineages as a hedge against extinction. A disproportionately large number of valuable medicinal and marketable compounds appear to exist in the Cape and coastal species, making their ongoing extinction a very practical loss of knowledge, human usefulness, and beauty. That is nothing to joke about.