This beautiful species occurs widespread from DR Congo and Tanzania to Sudan, Eritrea and Somalia on rocky slopes in wooded areas and cultivated lands at altitudes between 1200 and 2400 m.
It is also often cultivated as an ornamental as well as medicinal plant.
It has upright stems (often creeping at the base) 0.5-1.3 m. or more tall, with leaves up to 25 cm long and about 13 cm wide which are often marbled with brown to purple markings on both sides.
The inflorescences are 30 cm or more tall and the flowers are white (rarely cream), sometimes flushed with pale pink. The flower have long tubes, usually between 4.5 and 12 cm long.
There is only one place in the world where this species is known to occur: Tanjona Vohimena, the southernmost tip of Madagascar*.
On this stark, wind-swept limestone terrace about 100 m above sea level, the species occupies an area of less than a km².
Old plants possess a large turnip-shaped root to 30 cm long and to 10 cm wide, topped by a densely branched crown to 30 cm in diameter. In habitat the branches creep along the ground as a result of the constant wind; in cultivation they are more or less erect.
The leaves form rosettes at the tips of the branches, they are to 25 x 8 mm in size and green to red-brown.
* The old name for this is Cap Sainte Marie, which explains the specific epithet.
Plant in cultivation; scanned slide
In the dormant state, without leaves and flowers, this species is difficult to distinguish from P. densiflorum and P. rosulatum. They share the same habit: low, multi-branched shrubs up to 1.5 m in diameter and up to 1 m tall.
P. horombense is named after the Horombé plateau in the southern highlands of Madagascar, where it often occurs in great numbers on granite rocks.
The inflorescence has an erect peduncle of no less than 60 cm tall, with broadly cup-shaped flowers 1.7-2.3 cm in diameter.
According to Werner Rauh in his great book on the succulents of Madagascar, this is:
“the most beautiful Pachypodium species in cultivation”.
When one sees a great many of these plants together, this usually means that the local vegetation has been heavily disturbed (the plants are rarely eaten by stock or game because the juice in the leaves is very salty). They can absorb a great amount of water after rain, not only in the leaves but also in the roots.
The plants usually live for only a few years or, in more official terms, they are annuals or short-lived perennials, up to 50 cm tall with leaves 3-4 cm long and about 1 cm thick.
The flowers appear in spring (August-October) and produce large fruits with woolly seeds.
This species (the only one in the genus) is widespread on dry sandy or loamy flats from southern Namibia and Bushmanland to the Little Karoo.
The specific name echinatus means prickly or armed with spines or prickles and is derived from the word echinus (hedgehog).
When you look at the recurved thorny stipules on the stems, it is easy to see where the name comes from.
The plants may be up to 60 cm tall, but are usually much smaller; they have few to many branches, with leaves 2-3 cm long and 3-4 cm broad on relatively long stalks.
The flowers are about 3 cm in diameter and appear from July to November in groups of 3-8. They vary in colour from white and pink to brilliant purple, with darker blotches.
This beautiful and interesting species occurs from the Richtersveld to Clanwilliam,
usually on dry granite or sandstone slopes and protected by bushes or overhanging rocks.