– Euphorbia spiralis (2011)

By Mary O. Dasovich (October 2011)

Euphorbia spiralis is endemic to Yemen, specifically the island of Soccotra. Soccotra is one of four islands in an archipelago located in the southeast Gulf of Aden, Indian Ocean. It is the largest of the islands, 3,600 kilometers in size. Sparse and wind-swept, the island rises from sea level to 700 meters.

E. spiralis plants are succulent over most of Soccotra, with heavy populations on exposed parts of the limestone plateaus found on the island. If touring the island, they are first seen on the gravel and stone plains of the first major vegetative zone inward from the sea (Rhind). E. spiralis is the only spiral succulent found on the island. It was named by Edward Balfour (probably in the 1850s) based on his observation of the spiraling of its stems.

In native habitat, Euphorbia spiralis grows to heights of 6 to 12 inches. Its stems are small and globoid to columnar and grayish-green in color. While the plants we usually see have spiraling ribs, the ribs can be straight (Bramwell). Viewing live plants and pictures suggests the spiral can be either clockwise or counterclockwise. Leaves are small and deciduous with a leathery texture. The plants’ active growth period is late spring into the summer months.

Flower peduncles (stalks) are long and persistent with primary bloom time occurring in December in the Southern Hemisphere. The flowers are pale green in color and unisexual, generally reduced and grouped into pseudanthia (flower heads) called cyathia.

Each flower head consists of both male and female flowers, with the male flowers outnumbering the females. Female flowers carry three-part pistils located over three-part ovaries. Typically, female flowers produce three or more seeds.

Euphoriba spiralis is one of many plant species that have been subjected to aridity. Climate change over many years forced the plants to become tolerant of a reduced water supply. As a result, the plants are identified as drought resistant.

Also known as spiral spurge, they received the name spurge from the French “espurge” (to purge) because at one time, E. spiralis sap was used as a purgative. Spiralis enjoy full sun during the growth period and minimally bright light otherwise. However, they are somewhat cold hardy. They are said to prefer a pH between 6.1 and 7.8.

The plant I received as a premium plant at the July society meeting is doing well. It is responding to reshaping via the use of crushed foil to gradually move its offshoots into more balanced positions. It does demand sun, high light and more water than expected. It will be grown under greenhouse conditions over the winter with the hopes of having a show-worthy plant come next July.

Sources:
The Biology of Island Floras – Bramwell, David
Dave’s Garden – http://davesgarden.com/guides/articles/view/2326
Plant Formations in the Socotran BioProvince – Rhind, Peter Martin