Pachypodium horombense

Origin
Pachypodium horombense is endemic to South-Central Madagascar, specifically native to the Horombe Plateau (from which it derives its name) and the surrounding Isalo Massif. It was officially described by the French botanist Henri Jean Humbert in 1923.

Habitat
In its natural environment, this species thrives as a lithophyte on granite and gneiss rock outcrops. It grows at altitudes ranging from 500 to 1,000 meters in a sub-arid climate. The plants are typically found in cracks of sun-drenched rocks, where they are exposed to intense UV radiation, high temperatures, and strong winds. They have adapted to survive a long dry season by entering a period of complete leaf-loss dormancy.

Description
Pachypodium horombense is a spectacular pachycaul succulent, valued for its "squat" silver trunk and exceptionally large, ornamental blooms.

Caudex & Form: It develops a thick, globose to bottle-shaped caudex that is often very broad at the base. It is a dwarf species, usually staying under 1 meter in height but becoming heavily branched and "muscular" with age. The bark is a smooth silvery-gray, reflecting heat in its exposed habitat.

Spines: The branches are armed with paired, sharp, and sturdy stipular spines. These spines are typically shorter and more robust than those of the common P. rosulatum, giving the plant a more compact and "armored" appearance.

Foliage: The leaves are dark green, elliptical, and form dense rosettes at the tips of the short, thick branches. They are deciduous and shed during the winter dormant period.

Flowers: This species is famous for having some of the largest flowers in the genus. The blooms are a brilliant canary yellow, bell-shaped (campanulate), and appear on long peduncles. The inflated corolla base is a key distinguishing feature of this species.

Cultivation: This is a resilient and stable species in cultivation. It requires full sun to maintain its legendary silver skin and compact form. A very airy mineral substrate (e.g., pumice, lava rock, and coarse sand) is essential. It should be watered regularly in summer and kept warm and absolutely dry in winter.