Ascension spurge  (Euphorbia origanoides)

Classified as Critically Endangered (CR – B1+B3c) under IUCN Red List categories (3).

These dome-shaped plants are extremely attractive (2). The fleshy stems of the Ascension spurge are crimson in colour and contain a thick milky juice, which is poisonous and can cause blindness if it comes into contact with the eyes (4). The simple leaves are oval in shape and finely toothed at the edges; they are found in pairs at regular intervals along the stems (2). This genus is characterised by its extremely simple flowers. The reproductive shoot (inflorescence) is know as a ‘cyathium’ and consists of a spiral of bracts within which the simple male flowers are located. At the centre of the male flowers sits a single female flower. The structure of the cyathium is such that the cluster of simple flowers actually resembles a true flower from a distance (5).

Endemic to Ascension Island in the South Atlantic, 93% of the population is concentrated in the South Gannet Hill, Mars Bay, Cross Hill and Round Hill areas (3). Populations have undergone severe fluctuations in recent times and the current trend is unclear (3).

The Ascension spurge is found on some of the driest areas of the island, on larva plains up to 310 metres above sea level (3).

Very little is known about the natural ecology of the Ascension spurge.

The small range of its population threatens the Ascension spurge, which is extremely vulnerable to any chance event such as natural disaster or disease. Declines in colonies at Cross Hill have been attributed to the cottony cushion scale insect (Icerya purchasi) which has been introduced to the island (2). This spurge also suffers from competition with the introduced Mexican thorn (Prosopis juliflora), which spreads extremely rapidly (3).

Aspects of the ecology of the Ascension spurge are currently under investigation and a cultivated population has been established by Ascension Conservation (3).