Q.Once a Christmas cactus has begun to have buds can I put it in a cool dark place for 6 to 8 weeks?
This cactus is several years old and has flowered multiple times during the year. It summers outdoors in partial shade. We heat with wood and I want to protect it from too much heat.

Certified GKH Gardening Expert
If it's in bud go ahead and let it bloom. Normally, at 6 to 8 weeks before you want a bloom cycle, you would decrease water and light. Make sure it has 12 to 14 hours of uninteruppted darkness each day and cool temperatures about 50-55 F. (10-12 C). (put it in a room where the lights are not turned on in the evening) It does not need complete darkness.
Here is more:
https://www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus/advice-for-christmas-cactus-care.htm