The Obsidian Jewel: Euphorbia francoisii (Dark Foliage Form)

A collector-grade geophyte boasting architecturally distinct, deep-hued foliage that serves as a sophisticated focal point for any xeric collection.

1. Origin & History of Name The genus Euphorbia derives its name from Euphorbus, the Greek physician to King Juba II of Numidia (circa 50 BC), credited with discovering the medicinal properties of the plant's latex. The specific epithet francoisii honors Edmond François, a French botanist and horticulturalist active in Madagascar during the early 20th century. The species was formally described by Jacques Leandri in 1946, highlighting its significance in Malagasy flora.

2. Morphology This species is a dwarf, caudiciform succulent characterized by a thickened subterranean rootstock (caudex) that stores water. The "dark" phenotype exhibits leaves rich in anthocyanins, resulting in a striking deep purple to near-black epidermis. The leaf margins are often undulate (wavy), and the surface may display a cartilaginous texture. Unlike typical succulents, its primary appeal lies in this foliar polymorphism rather than its modest, yellow-green cyathia (inflorescences).

3. Habitat & Origin Euphorbia francoisii is endemic to the dry deciduous forests and shrublands of Southern Madagascar, specifically the Taolagnaro region. While critically endangered in the wild due to habitat loss, the specimen offered here is a nursery-propagated cultivar. This ensures zero pressure on wild populations and guarantees the genetic stability of the dark leaf coloration through ethical ex-situ conservation.

4. Cultivation Profile

• Substrate: Use a highly porous, mineral-heavy mix to prevent root rot. A recommended ratio for Indian climates is 70% inorganic (pumice, perlite, or gravel) to 30% organic matter (coco-peat or compost).
• Light: Requires bright, filtered light to maintain deep leaf coloration. In the harsh Indian summer, avoid direct noon sun which can scorch the epidermis; however, insufficient light will cause the leaves to revert to green.
• Water & Dormancy: Water thoroughly when the substrate is completely dry. In Indian conditions, strictly reduce watering during the monsoon season to prevent fungal issues and during winter dormancy when leaf drop may occur.

5. Scientific Anecdote Euphorbia francoisii is renowned among botanists for its extreme phenotypic plasticity—the ability of a single genotype to produce different phenotypes. In the wild, leaf shapes can vary from linear to broadly ovate within the same population, a trait that has allowed modern breeders to isolate and stabilize spectacular forms, such as this dark-leaf variety, without hybridization.