The usually only one central spine is initially protruding, later directed downwards, strong, needle-like and up to 5 cm (2.0 in) long.

The white flowers are dark purple on the outside and have a greenish-white to red throat.

[3] This species is extremely variable, and different populations have been described as distinct species The following are recognized subspecies:[2] Haageocereus pseudomelanostele is found in the Peruvian regions of Ancash, Ica and Lima at altitudes of 300 to 2000 meters.

The first description as Cereus pseudomelanostele was made in 1932 by Erich Werdermann and Curt Backeberg.

(1932, incorrect name, ICBN article 11.4) and Echinopsis pseudomelanostele (Werderm.