A tree-like euphorbia

First described in 1791 by the German botanist Johann Gmelin, Euphorbia abyssinica is endemic to Ethiopia, Somalia, Sudan and Eritrea. It is a succulent, tree-like euphorbia, towering up to ten metres tall and forming either large stands or growing as solitary plants in montane woodlands, scrub savannah and on arid hillsides. Cactus-like in appearance, Euphorbia abyssinica is adapted to these dry tropical habitats to conserve water and survive extended periods of drought.
The thick, green main trunk, which becomes woody with age, supports many 5-8-angled, branching stems. The species has developed the capacity to store water in its stem tissue and is also able to photosynthesise effectively through the surface tissue of the stem. Leaves form on young growth at the end of the branches but fall in the dry season.
At intervals along the stem angles or ribs are small, rounded structures from which leaves, flowers or spines may grow. In succulent euphorbias the spines are paired, whereas in cacti spines are either singular or held in groups of three or more.
A distinguishing characteristic of euphorbias are the cyathia. These tiny cup-shaped structures bear the very small, modified male and female flowers.
The male flowers of Euphorbia abyssinica are reduced to a single stamen and the female flowers consist of a stalked pistil with branched stigmas. The flowers are without petals, but are surrounded by noticeable yellow bracts. Tiny glands producing a nectar reward for would-be pollinators surround the flowers. The fruit is a capsule up to two centimetres long, which, as it ripens, explodes scattering the seed across the ground.
Euphorbia abyssinica has toxic milky sap that causes irritation and blistering if it comes into contact with the skin. The sap can also cause temporary or permanent blindness if it comes into contact with the eyes.
In Ethiopia, the sap has been used mixed with butter as a topical treatment for fungal skin infections. It is also used by traditional healers in the treatment of malaria and visceral leishmaniasis. Euphorbia abyssinica is used for firewood and provides timber for furniture and roofing. Studies have shown the sap can promote rooting in cuttings of other species such as the threatened tree, Boswellia papyrifera.
All succulent species of Euphorbia are listed in CITES (Convention on International Trade in Endangered Species), an international agreement that governs the trade in plants to ensure their survival into the future is not threatened.