Do not be fooled by the common name Madagascar palm, as this tree-like deciduous succulent plant belongs to the dogbane family, Apocynaceae, not the palm family. Two species of Pachypodium native to Madagascar are called by this name, as well as clubfoot. Grow them outdoors only where winters are mild but elsewhere as a house plant while they remain small.
Sixteen species of Pachypodium exist in the world, but only two commonly grown in gardens and conservatories receive the moniker Madagascar palm: Pachypodium lamerei and Pachypodium rutenbergianum. All species develop elephant leg-like trunks that bear clusters of protective spines.
Native to the semi-arid, limestone-based gritty soils of southern Africa, both species of Madagascar palm hail from southern Madagascar Island. Nine other species of Pachypodium also grow naturally in Madagascar and five species in Namibia.
Pachypodium lamerei grows to a mature height of 18 feet with a trunk that looks bottle- or barrel-shaped, especially at its base. Spines occur in clusters of three all over the trunk. The long, narrow, glossy dark green leaves appear in tufted clusters at branch tips, falling away in fall and winter during the cool dry season. In the warmth and rains of summer, the leafy branch tips bear clusters of white, fragrant, trumpet-shaped flowers with five lobes, resembling the blossoms of a frangipani (Plumeria spp.). Branches develop from the flower cluster tips after the blossoms fade and drop away.
Pachypodium rutenbergianum grows to 15 feet in mature height with a thick, elephant leg-like trunk that displays singular spines, sometimes in pairs all over. On old plants, the spines disappear from the trunk base and protect only the upper branches. The deep green, lance-shaped leaves grow in whorled tufts at branch tips and drop away in fall as the dry season begins. In the middle of the winter, clusters of fragrant white flowers with five twisting lobes decorate branch tips when no leaves are present.
Grow all Madagascar palms in abundant sunlight, no less than eight hours of direct sun rays daily. The soil must be coarse, gritty and fast-draining regardless of pH. When leaves appear and grow in summer, provide 2 to 3 inches of water every two weeks and cease all watering from the autumnal equinox onwards until the vernal equinox. Any application of fertilizers must occur only in summer with leaves present. Compost atop the root zone benefits the plant and can be applied anytime of year.
The spines on the trunks remain rigid and steadfast even after being touched, adding to the discomfort when you accidentally nudge into them. The clear sap of broken leaves and branches irritates skin and must not be allowed to enter open skin wounds or eyes and certainly not eaten.