I induce flowering on outdoor container plants by moving them indoors for 12 hours of darkness. It works fine and also allows me to have two summer harvests. I start flowering first crop in a couple of weeks.
I will start 2nd crop soon for flowering to begin in last week of July.
I also move ALL of my outdoor container plants indoors to controlled climate to prevent Bud Blight and powdery mildew from ravaging my girls.
My area is very humid.
good luck!