Origin and Habitat: Haageocereus pacalaensisSN|5657]]SN|5657]] subsp. repens is endemic to a small area 10 to 14 km south of the city of Trujillo, Region La Libertad, Peru.
Altitude range: 50-300 metres above the sea level.
Habitat and ecology: Haageocereus pacalaensisSN|5657]]SN|5657]] subsp. repens grows prostrate on the sand near the coast of Trujillo. This Trujillo taxon is seriously threatened by an irrigation project (Chavimochic) and it is a matter of time to be replaced by an asparagus cultivation. The subsp. pacalaensis is critically endangered, but some of the plants have been rescued by the professors and students of the National University of Trujillo in 2005 and are planted in the campus of that University. As the entire original habitat of Haageocereus pacalaensisSN|5657]]SN|5657]] subsp. repens is rapidly being degraded or flooded for the irrigation project, a reintroduction within its habitat is not planned. However, it should be evaluated whether it can be introduced into another suitable area.

• Haageocereus pacalaensis subs. repens (Rauh & Backeb.) Ostolaza
• Haageocereus pacalaensis var. repens (Rauh & Backeb.) Krainz
• Haageocereus repens Rauh & Backeb.

• Haageocereus pacalaensis Backeb.
• Binghamia pacalaensis (Backeb.) Werderm.
• Cereus pacalaensis
• Haageocereus horrens Rauh & Backeb. in Backeb.
• Haageocereus horrens var. sphaerocarpus Rauh & Backeb.
• Haageocereus laredensis Backeb. in Backeb. & F.M.Knuth
• Binghamia laredensis (Backeb.) Werderm.
• Cereus laredensis
• Cereus pseudomelanostele var. laredensis Backeb.
• Haageocereus pacalaensis var. laredensis (Backeb.) Krainz in Krainz
• Haageocereus pacalaensis var. longispinus (Rauh & Backeb.) Krainz in Krainz
• Haageocereus laredensis var. longispinus Rauh & Backeb.
• Haageocereus tenuispinus Rauh & Backeb. in Backeb.

• Haageocereus pacalaensis subs. repens (Rauh & Backeb.) Ostolaza
• Haageocereus pacalaensis var. repens (Rauh & Backeb.) Krainz
• Haageocereus repens Rauh & Backeb.

Description: Haageocereus pacalaensisSN|5657]]SN|5657]] subsp. repens is a rare cactus species often included within (as a synonym of) Haageocereus pacalaensisSN|5657]]SN|5657]], but distinguished by cylindrical stems crawling horizontally on the sand with ascending apexes (The stems in the standard H. pacalaensis are erect and easily tell apart at a glance).
Stems: Prostrate, decumbent, up to 2 m long, 8 cm in diameter, with the raised apex.
Root: Napiform root and adventitious roots along the branches.
Ribs: 18.
Radial spines: 40 thin, amout 1 cm long.
Central: 1 to 2, up to 1.5 cm long.
Flowers: White, 7 cm long, 3.5 cm wide.
Note: This South American species has developed a prostrate growing habit similar to that of the 'creeping devil' Stenocereus erucaSN|7988]]SN|7988]] in North America.

Bibliography: Major references and further lectures
1) Carlos Ostolaza Nano “Todos los cactus del Perú” December 2014
2) Arakaki, M., Ostolaza, C., Cáceres, F. and Roque, J. “Cactaceae endémicas del Perú.” Revista Peruana de Biología 13(2): 193s-291s. 2006.
3) Ostalaza, C., Cáceres, F. & Roque, J. 2013. Haageocereus pacalaensis. The IUCN Red List of Threatened Species 2013: e.T152353A627212. http://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T152353A627212.en. Downloaded on 14 December 2016.