This succulent shrublet has a swollen tuberous main stem and a number of short spiny branches, each bearing a rosette of leaves. They have a single long-pedunculate inflorescence that carries 3-10 broadly cup-shaped chrome-yellow flowers between April and August. The flower has an inflated corolla that forms five large sacs into which the pollinator can crawl. The epithet refers to the Horombe plateau in southern Madagascar where the type specimen comes from. Here it grows on granite rocks at altitudes of 500-1 000 m. It is impossible to distinguish it from P. rosulatum when not in flower.
U.S. SHIPPING ONLY Plants are individually boxed and ship bare root, pot/soil not included