Etymology -From the Greek "lasios", meaning woolly - therefore woolly cereus
Two species make up the genus Lasiocereus and this treatment is fairly consistent across various authors. This apparent agreement is not the result of there being a complete understanding of the genus, but just the opposite. It seems these two species are left alone more for the fact that there is not a better place to put them. Hunt speculates in The New Cactus Lexicon that the two species may be hybrids within the Trichocereeae, but this is not much more than a suspicion.
The plants themselves are characterized by having cylindrical stems with numerous ribs, closely-spaced areoles with spines that are clearly visible, but not so numerous as to obscure the stems. Flowers come from woolly sections of the stem that are not developed enough to be a true cephalium. The flowers themselves are tube-shaped, nocturnal and white. The floral tubes feature both wool and bristles and are wide in proportion to their length when compared with flowers of similar plants.
Lasiocereus occur only in Peru and are quite similar to Haageocereus, which also occurs in that region. In cultivation, this genus is almost non-existent - appearing occasionally in a botanical collection or on a seed list.