Does not matter I think, they want to sleep in winter. They just know they have to. Sure comfortable for humans..but not for Adeniums. I think it is the combination of light and temperature, but who knows, I don't have a greenhouse, I just haul them indoors. Something I realize now, why do I want them to be awake in winter when it naturally wants to sleep, to preserve itself.They will just come back later on in late Spring anyways, just have to keep them safely warm without getting too dried out especially when they are still babies.
