Etymology From the Greek - pilosus -meaning hairy cerues.
The genus Pilosocereus was known as Pilocereus up until 1954 when it was renamed due to a discrepancy found according to the rules of botanical nomenclature. This earlier name meant felted-cereus. Both names refer to the very hairy areoles on the stems - at least the mature flowering portions of the stems. Many of the species in the genus feature spectacular blue-colored stems, but may be green. Plants are either shrubby or large, tree-like. Flowers are tube-like and the floral tubes and unopened buds are often very blue in color. The perianth parts of the flower are often white or pinkish-white with many stamens and a protruding style. Floral tubes have scales and are smooth and spineless. Pollination is done by bats. Fruits are fleshy and contain seed and pulp.
In the wild, this genus is widespread from Mexico and in the Caribbean Islands, down throughout South America. A few species are known in cultivation, while others species by contrast can scarcely be found using an internet image search. Of the species in cultivation, P. pachycladus is produced on a massive scale by large wholesale nurseries. Presumably for the attractive blue skin. As a result, it is one of the most common cactus species in cultivation, next to the "Golden Barrel" - Echinocactus grusonii. It is often sold under the more pleasant sounding synonym P. azureus.