Euphorbia stenoclada aka Silver Thicket

Euphorbia stenoclada Baill. is a succulent shrub in the family Euphorbiaceae (Malpighiales), described by Henri Ernest Baillon in 1887 (Bull. Mens. Soc. Linn. Paris 1: 672). It is most commonly known by the English vernacular name silver thicket. The species is endemic to Madagascar and the small Mozambique Channel Islands of Europa, and Plants of the World Online also records an introduced occurrence in Spain.

In its native range Euphorbia stenoclada is a characteristic plant of dry, sun-baked landscapes. POWO classifies its biome as desert or dry shrubland, and the wild populations grow in subtropical and tropical dry forest, dry shrubland, and rocky areas. The species is one of the iconic components of the Madagascar spiny thicket, where stands have been documented near Mangily in the southwest of the island. Two subspecies are recognised by POWO: the typical Euphorbia stenoclada subsp. stenoclada and Euphorbia stenoclada subsp. ambatofinandranae (Leandri) Cremers. The only listed taxonomic synonym is Tirucalia stenoclada (Baill.) P.V.Heath.

Like many stem-succulent Euphorbia species from the Malagasy spiny forest biome, E. stenoclada has a tree-like to shrubby succulent habit; POWO summarises the lifeform simply as "succulent shrub". The genus is well known for its caustic milky latex, but specific morphological details for E. stenoclada (height, branching pattern, spines, leaves, flowers) are not provided in the authoritative taxonomic sources fetched here.

The plant has a documented place in Malagasy ethnomedicine: it has been used traditionally as a remedy against asthma and acute bronchitis. A peer-reviewed study by Chaabi and colleagues (Journal of Ethnopharmacology, 2007) showed that an ethanolic extract abolished interleukin-1beta-induced proliferation of cultured human airway smooth muscle cells, and identified the flavonol quercetin as the active anti-proliferative compound. The authors proposed that quercetin's presence helps explain the traditional respiratory use of the plant.

In conservation terms, Euphorbia stenoclada is currently treated as Least Concern under IUCN 3.1, but Wikipedia notes that the species is threatened by habitat loss in its native range. There is no record of E. stenoclada in invasive-species databases such as the IUCN Global Invasive Species Database, and POWO lists only one introduction (Spain), so the species is not regarded as weedy outside its native range.