Pilosocereus

Pilosocereus (from Latin, "hairy cereus") is a genus of cactus native to the Neotropics. Tree cactus is a common name for Pilosocereus species. The genus Pseudopilocereus is a synonym of this genus. For many years, the illegitimate name Pilocereus was used for this genus, although properly a synonym for Cephalocereus. The subdivision of the genus has varied very widely, resulting in very different numbers of species being accepted. The commonly cultivated Pilosocereus pachycladus (syn. Pilosocereus azureus) is a blue cactus with hairy areoles that emit golden spines....read more on Wikipedia.