Any of various large cacti (genus Cereus and related genera) of the western U.S. and tropical New World, including the saguaro and the organ-pipe cactus ( Lemairocereus thurberi , also L. marginatus or C. thurberi ).
The genus Selenicereus (night-blooming cereus, or moon cactus), containing about 20 species, is known for its large, usually fragrant, night-blooming white flowers, among the largest in the cactus family. The queen-of-the–night ( S. grandiflorus ), the best-known night-blooming cereus, is often grown indoors.