Christmas Cactus are tropical, like Orchids and Bromeliads, and they require a dry period several weeks prior to the time when you want them to bloom in order to set flower buds. The following document link has some good information and a timetable that you can use as a guide: http://www.horticare.net/PDF%20Files/UsefulGardeningInfo/CHRISTMAS%20CAC....

Thanks for your inquiry,

Happy Gardening!
The PlantMaster