To take care of a Christmas cactus, place the plant in an area with bright, indirect light, and keep a source of humidity nearby when growing the cactus indoors. Fertilize the plant with a low-nitrogen fertilizer, and water the plant when the top inch of soil feels dry. Place the plant in a room with at least 12 hours of complete darkness and 12 hours of sunlight six to eight weeks before Christmas to force blooming.
Beginning in early autumn, water the cactus sparingly, maintain a temperature of approximately 50 degrees Fahrenheit in the plant's room, and do not expose the plant to artificial lights at night to force the plant to bloom. When Christmas season is over, allow the cactus to rest for 30 days in a cool location, and continue to water the cactus sparingly.
To provide the plant with the proper humidity, place a container of water or a humidity tray near the plant. Do not overwater the cactus, as this can cause the blooms to drop off the plant prematurely.
Prune the cactus during the early spring, and place the cactus and its container outdoors in a sunny location during the summer months. If stem or root rot is present, cut away the damaged parts of the plant, and replant the cactus in a container with new soil.