If you have a TRUE Xmas cactus, it should be sitting down the basement, near a window *right now*. Leave it there with no other light and no water until the middle of December and you should have blossoms. I find a combination of cold, long dark times, no artificial lights and dry soil make my 30 year old plant bud.

Then there was one winter when I kept it near a wood stove in a cold, but window filled loft in my cabin. I used to cast water on the wood stove to create steam for all the plants to enjoy when the stove was going. That Xmas the cactus bloomed from December until after Easter -- four months and hundreds of blossoms.