I have used the ice cube method actually, but only in the height of our dry summer a few years ago. Never on colder seasons. Seems to help the plant a bit. I just make sure the ice cube is on the media, and not on any exposed root as it slowly melts. Does it spike later because of that..not sure though, since it naturally gets cooler here. But I don't do it anymore, it will do the spike when it is ready, and always when it has cooled down all over.
