The 12 to 14 ribs are initially notched and later divided into clear cusps.

[4] The broad, funnel-shaped, scented, white flowers are around 15 cm long.

The plants grow very slowly and in cultivation require very well-draining growth media to avoid rots.

The epithet of the species is named after the British cactus collector Ronald S.

[4] Pygmaeocereus bylesianus is common in the Peruvian region of Arequipa at altitudes of 50 to 1000 m. This ground is extremely dry and condensation of fog is the major source of water.