When visiting California a couple months ago, one of the highlights of the garden tours was the chance to visit the Desert Garden Conservatory at Huntington Botanical Garden (it had been closed during my previous visit to the garden). It contains an outstanding collection of plants, including this desert rose.
Adenium obesum is a member of the widely-distributed dogbane family, or Apocynaceae. It is native to eastern and southern tropical Africa, as well as the Arabian peninsula.
You’ll note the thickened stem, a trait which grants desert rose membership into an informal grouping of plants called pachycauls (literally, “thick stemmed”). It can also be called a caudiciform, due to the particularly swollen stem at the base (the caudex). Water storage is generally the strategy behind this mode of growth.