Christmas cactus needs short days and cool night temperatures in order to bloom. Bright light, high humidity, and soil that’s kept slightly moist most of the year are all essential as well. To keep the bright blooms after the holidays, follow these tips:
Keep it in the dark. Don’t keep it in a room where lights are on well into the evening. Move it to a dark space or cover it with a dark plastic trash bag so no light reaches it for 12 or 13 hours each night.
Don’t prune the flat, arching stems (buds form on the tips), and don’t fertilize so heavily that you encourage only vegetative growth.
For next year’s blooms, leave your cactus out in the summer months. Place it in a spot where it is protected from strong mid-day sun. Leave it there as late into fall as possible, bringing inside only when frost threatens.
Bring indoors. When you bring the cactus indoors, place it in a bright window where temperatures drop to 55°F to 60°F at night. If nights are a bit warmer (65°F or so), it will take longer for buds to develop.