Pilosocereus polygonus

Pilosocereus polygonus is a species of cactus (family Cactaceae). Like all species in the genus Pilosocereus, it has a shrub- or tree-like growth habit. It has been treated very differently at times. In the narrow circumscription adopted here, it is endemic to Hispaniola, a position adopted by Britton and Rose in 1920 and endorsed in a 2019 review of the genus in the Caribbean and northern Andes. Treatments in the late 1990s and early 2000s used a much broader circumscription, which included species now recognized as separate, thus giving P. polygonus a much wider distribution. As of July 2025, Plants of the World Online accepted Pilosocereus royenii as a synonym; however it has also been treated as a separate species. Broadly applied English names include dildo cactus, pipe organ cactus, and Royen's tree cactus.