Selenicereus is a genus of a few dozen climbing, lithophytic or epiphytic cacti with big (to giant) nocturnal flowers and globose or oblong, fleshy, usually red fruit.

Selenicereus (formerly ~28 species with narrow, 2-12 sided stems) recently absorbed the genus Hylocereus (~18 species, typically with 3-sided stems) and most of Weberocereus (~5 species with 2-5 sided stems), based on DNA sequence analysis. The former Hylocereus, and possibly some other plants, is referred to as pitahaya, as is its fruit, in Mexico and other countries of origin. These cacti are cultivated for their fruit, most notably Dragon Fruit (Selenicereus undatus), as well as their large nocturnal flowers (the largest in the family). The new Selenicereus spans a geographical range from the southern US through Mexico and Central America and the Caribbean, into northern South America.

The closest genetic relatives of Selenicereus include Disocactus, Epiphyllum, Kimnachia, Pseudorhipsalis, and Weberocereus (in its newly reduced form, with 2 species). The 2017 study which expanded Selenicereus can be found here:

https://www.researchgate.net/p...

Note: the pitahaya (Selenicereus, climbers and epiphytes) is distinct from the pitaya (Stenocereus, spiny columnar cacti), though the pronunciation is nearly the same. Both words refer to the edible fruit and the plant.

Reply to this comment