Pachypodium rosulatum v. gracilis Seeds - Succulents

In elevation, Pachypodium in both mainland Africa and Madagascar grow between an altitude of sea level, where some species grow in sand dunes, such as Pachypodium geayi, to 1600 m (5200 feet) for Pachypodium lealii in southern Africa and 1900 m (6200 feet) for Pachypodium brevicaule in Madagascar.

A generalization about precipitation regimes for both southern Africa and Madagascar does not have much meaning because the habitats of Pachypodium vary so greatly with a moisture regime. In some places, Pachypodium receive annually from as little as 75 mm (2.95 inches) from the southern part of Africa to a high level of 1985 mm (78.15 inches). A precipitation regime for a species of Pachypodium, therefore, depends upon a habitat's location relative to the influences of the Atlantic and Indian Oceans and the various mountain ranges of southern continental Africa and of Madagascar.
The genus grows in areas where there are significant periods of dry months that range from five months to ten months.

Pachypodium grows in various types of substrates. Some species only grow in one substrate whereas other will grow in several. The degree to which a taxon can grow in a given substrate seems to determine how specialized its habitat is within the landscape and climates. On outcrops, steep hills, and inselbergs, the plants are subjected to fluctuating moisture, high winds, and temperature extremes. Only plants with special adaptations to exposure and extreme drought can survive, let alone thrive, on these exposed geological habitats. Pachypodium root in cleft, fissures, and crevices of those rocky formations. The non-succulent roots penetrate deeply into the acuminated soil, mineral, and humus in these crevices. Moisture is able to seep deep into these crevices. Very little transpiration occurs. In this manner, rocky substrates provide moisture in the habitat. This saturation of crevices can only occur, however, if there is not a considerable runoff from the rock's surface and if there is abundant fine soil in the cracks that, in turn, retain water. The substrate, therefore, plays a critical role in the creation of micro-environmental "arid islands."
Sand readily store water because it is taken up easily and there is less evaporation except for the top layer. Very deep sand; however, has the problem of seepage. Yet in moderation shallow and deep sand substrates have water available to Pachypodium. With shallow sand substrates, Pachypodium grow on sand dunes near the sea. Where water is in deep sandy substrate, Pachypodium grow on sand "over" laterite red soil. Laterite soil is a largely impermeable soil that traps water for the use of the flora that include Pachypodium.