Surely you would need to ask if Nadia wants the cultivar name (or Nadia, do you just want confirmation that is is Epiphyllum?). There are Epiphyllum named 'Yellow', 'Yellow Wish', 'Yellow Delight', 'Yellow Florence', 'King of Yellows'; also yellow are 'Candice', 'Jennifer Anne', 'Desert Falcon', 'Kiwi John Boy', 'Vista Sun', 'Andromeda'. Common name seems to be orchid cactus, because it blooms in trees along with orchids, though one site says it's because the blooms resemble some orchids, which seems questionnable.
I am not sure if they know. It is not like the Bloedel Conservatory, just some room in the office-shop place, no labels were there on any plants. I need just a general name, not specific. It looks to me like Epiphyllum.
