If your Christmas cactus has pink buds at the ends of its stems, leave the coffee grounds in the kitchen. The plant has already started making flowers. A draft, a blast from a heating vent or a pot that dries out can cost you those buds before they open.
When you can see buds, keep the plant’s routine steady
Keep the cactus where it gets bright, indirect light and where temperatures stay stable. Move it out of the path of a heater or a door that lets in cold air. Check the potting mix by touch before watering. When the surface starts to dry, water and let the pot drain. Empty the saucer so the base of the pot stays out of standing water.
University of Florida Extension points to changes in temperature and poor watering as causes of bud drop. Clemson Extension recommends keeping the potting mix moist after buds set and stopping fertilizer in late summer to support fall bud production.
If there are no buds, check the room after dark
Holiday cacti form buds in response to long nights or cool conditions. Think about when the room goes dark. A lamp beside the plant or light from an adjoining room can interrupt the dark period. University of Minnesota Extension explains the timing for Christmas, Thanksgiving and Easter cacti, which can flower at different times even when they look alike.
Save the grounds for compost
Used grounds do not give you a measured dose of fertilizer. Washington State University Extension recommends composting them instead of using them as a direct soil amendment. When the cactus is back in active growth, use a balanced houseplant fertilizer at the rate and season recommended by your extension guide.