Genus Pachypodium Characteristic

All Pachypodium are succulent plants that exhibit, to varying degrees, the morphological characteristics of pachycaule trunks and spinescence. These are the most general features of the genus and can be considered distinguishing characteristics.
The pachycaule trunk is a morphologically enlarged trunk that stores water so as to survive seasonal drought or intemitent periods of root desiccation in exposed, dry, and rocky conditions. Whereas there is great variation in the habit of the plant body, all Pachypodium exhibit pachycaul growth. Variation in habit can range from dwarf flattened plants to bottle shaped shrubs to dendroid-shaped trees.
The second general characteristic of Pachypodium is spinescence, or having spines. The spines come clustered in either pairs or triplets with these clusters often arranged in rings or whorls around the trunk. Spines emerge with leaves, and like leaves grow for a short period before stopping growth and hardending. Spines do not regenerate so weathering and abrasion can wear away all but the youngest spines from older specimens - leaving smooth trunks and branches.
To some extent, branches are a characteristic of the genus. Some caution is warranted in over-generalizing this characteristic. Pachypodium namaquanum is often branchless. Pachypodium brevicaule has no clear branches, and indeed may have evolved an alternative to branching in the form of nodes from which leaves, spines, and inflorescences emerge. In general Pachypodium have few branches. Since the environmental stresses and factors that contribute to branching can vary widely even in small areas, individual plants of the same species exhibit wide variation in branching morphology.
Unlike many members of the Apocynaceae, including some members of the superficially similar Adenium, Pachypodium species do not exude a milky latex. Rather, the sap is always clear.