Madagascan ocotillo (or arbre pieuvre in French) is native only to Madagascar. Five other species are known from the genus, and they are all southwest Madagascan endemics as well. Its family, the Didiereaceae, contains somewhere around twenty species (depending on your taxonomic perspective, it seems), some of which can be found on adjacent continental Africa.
Alluaudia procera and its kin are foundational components of Madagascar’s spiny thicket ecoregion. Forty-eight percent of the genera and 95 percent of the species occurring in the ecoregion are endemic to the island–one of the highest levels of endemism of living species on Earth.
This species is classified as Near Threatened by the IUCN Red List. Although it resembles a cactus, instead of having succulent tissues its trunk is woody. Wood from Alluaudia procera is used for construction and fuel (primarily as charcoal). Upon deforestation, its habitat tends to be replaced by grassland for cattle-grazing or maize production.
Plants can grow up to 15m (50 ft.) tall, and as displayed in the second photograph from the LA County Arboretum, the trunk can be free of branches for a significant portion of its length. Trunk diameters can reach 55 cm or 1.8 feet!
Via Pacific Horticulture, read more about the Madagascar Spiny Forest Garden at Los Angeles County Arboretum and/or visit The Danger Garden blog: A visit to the Los Angeles County Arboretum and Botanic Garden.