Etymology - Named in honor of Walther Haage, a German authority on cacti.Haageocereus species feature cylindrical stems with numerous shallow ribs with heavily-spined, closely spaced areoles. In many species, the spines obscure the stems. The overall growth may be erect, shrubby columns or prostrate stems, crawling along the ground as they grow. Flowers are funnel-shaped and the floral tubes feature both scales and hairs to varying degrees in the species. All are night-blooming, but do remain open into the day. As expected with night-blooming cactus, flowers are mostly white and fragrant. Some may be pinkish-to red. Fruits are globular and fleshy.
Populations of this genus are restricted to the Pacific coast of Northern Chile and Peru where they survive in one of the harshest environments on Earth with poor soil and little if any rainfall. Not surprisingly for cactus, the taxonomy within the genus is poorly understood and much more research is needed.
Plants in Haageocereus are nearly non-existent in cultivation and encountered rarely among extensive botanical collections or highly-specialized growers. with that said, there has appeared a plant in garden centers recently that some suspect is a Haageocereus species, while others contend that it is the more common Cliestocactus icosagonus. Based only on the stem characteristics, it is not possible to determine the identity with certainty. As of yet, these plants have not flowered. With a flower, the debate will be settled quickly as the flowers between these genera are quite distinct.