Adenium obesum, commonly known as the Desert Rose, is a flowering succulent related to the oleander and the plumeria. As a succulent, it thrives in extremely well drained and coarse planting mediums and will easily succumb to root rot when planted in regular garden soil or potting mix. Often grown in containers when small, adenium roots grow quite large in relation to the plant top.
Since adenium is native to the soil of sub-Saharan Africa and the Arabian peninsula it prefers lightweight, sandy and coarse soil. Add organic coarsening agents to the planting bed up to one third of the volume of planting soil. Use clean sharp sand, poultry grit, gravel or even horticultural charcoal or lava rock to make the planting soil free draining.
Use a commercial succulent or cactus potting mix as the basis for the planting medium for your adenium. It can be amended with a few other ingredients to make it even more free draining but will provide a good foundation for growing the moisture sensitive plants.
Perlite or sponge rock is a lightweight, coarse planting material that aids water drainage and remains lightweight even when used in large volume. Add perlite grains to the adenium planting soil to compose up to 1/3 of the overall planting soil soil volume. This addition will help to ensure that the adenium roots are never sitting in waterlogged soil and that tender young roots can easily penetrate the planting medium.