Without flowers, this species is similar to two others (P. horombense
and P. rosulatum), but they are easy to tell apart when flowering.
The plants are widely distributed in the central highlands of Madagascar, where they are often abundant in thick layers of black humus on inselberg slopes and rocks at altitudes between 200 and 1750 m.
They grow into shrubs of 10 to 50 cm tall and 1.5-2 m in diameter.
The branches are densely covered with pairs of spines and each has 3-5 deciduous leaves (to 10 cm long and 5 cm wide).
The inflorescences are 25 to 40 cm tall, with up to 30 flowers at the same time.
