Pachypodium is a genus of spiny trees and shrubs native to Africa, with 20 of 25 known species native to Madagascar. The other five species are native to continental southern Africa. The genus name means “thick-footed,” referring to the thick, succulent trunks that serve to store water and nutrients for times of drought. The trunks of all Pachypodium species are covered with spines growing in bunches of two or three, though the spines may be worn away and do not regenerate, leaving a smooth trunk. The spines, like the thickened trunk, are an adaptation allowing the trees to survive very dry climates, as they serve to collect moisture from dew and mist.
Outside of thick, spiny trunks, Pachypodium species exhibit great variety. Some species are flattened dwarf trees, and some have no branches. Some species have bottle shaped trunks, thick at the bottom, but thinning near the top.
P. baronii, commonly called Madagascar palm or bontaka, grows only on the western side of Madagascar on gneiss, granite, or calcareous rock. It has a short, bottle-shaped trunk, cylindrical branches, and red flowers with a yellow center. The spines are red and hairy when young, maturing to brown, smooth structures. P. lamerei may also be called Madagascar palm. It features fragrant, white blooms, though it rarely flowers when kept indoors.
Some other Pachypodium species endemic to Madagascar are P. ambongense, P. bicolor, P. brevicaule, and P. geayi. P. ambongense, also called songosongo or betono in the Malagasy language of Madagascar, is one of the rarest species. P. bicolor grows on sandstone and has greenish red, hairy flowers. P. brevicaule, which also grows on sandstone, is a dwarf species with a very flat trunk. P. geayi is one of the tallest Pachypodium species, featuring a metallic gray trunk and white flowers.
P. lealii, commonly called bottle tree due to its bottle-shaped trunk, is endemic to southern Angola and Namibia. It produces white flowers and a toxic, watery latex sap used by indigenous people to poison arrows for hunting. P. namaquanum, with the common name Halfmens, grows in Namibia and South Africa. It is one of the branchless species of Pachypodium and features red, velvety flowers that bloom in the fall.
Two very similar species, P. gracilius and P. horombense, are both found in Madagascar and Africa. They have short, fat trunks and large, yellow, bell-shaped flowers. Both plants are sometimes considered to be varieties of the species P. rosulatum.