It is a dream come true . I don't know what triggers this cactus to bloom . I observed the flower bud everyday. But just when I lose sight of it, the flower bloomed. A shy guy indeed . It bloomed together with my Phal Kenneth Schubert. But then I got a lot of "visitors" such as grasshopper and beetle since they bloomed. It is very unlikely to find these insects here and there was none coming before . Hopefully they will not harm my plants.
Enjoy the picture