In the past, I've overwintered my adeniums in the house. The larger ones I'd let to dormant in a closet with very, very little watering. The smaller ones were kept growing under lights with a heating mat to keep them warm. This year, my collection has grown so much that I don't have the enough room in the house. So I did a quick covering for the DRs outside: 2 sawhorses topped with a chain-link gate and covered with plastic to the ground. Inside, I have concrete pavers on the ground and dark-painted gallon jugs filled with water to hopefully keep some of the warmth during the night.
So far, the DRs seem to love it in there. The daytime temps are in the mid 80's. The DRs are blooming as much as if it were still summer. On really warm days, I lift one of side to reduce the heat buildup.
My concern is nighttime temps. While it seldom gets below freezing in New Orleans, we do frequently get temps in the low 40's to mid 30's. I do have a small electric heater that I can put in the "greenhouse" for warmth at night. So far, the lowest nighttime temp inside has been in the mid 50's. Is this too cool for the DRs? What would be a good minimum temp for them?
Jo-Ann