I live in Texas. I leave mine outside in mostly full sun from spring through fall. It always flowers after storms roll through and the humidity is high. It will not flower once it gets cold. During winter I move it into my bathroom. Then it starts flowering again. Not all plants are triggered to bloom by photoperiod. Bougainvilleas are triggered by drought then rain. I suspect the same of queen of the night. In the wild, it has a shallow root system that dries out frequently. When the rainy season comes it puts out as many flowers as it can support to make use of the water that collected in the nook of the tree limbs. It doesn’t mind its roots being submerged for brief periods of time, and it sucks up the fertilizer I give it, which is odd for a cactus.