This is the propagator tray where my Lithops (Living Stones) live:
There is a heating element built in the bottom of the tray which is controlled by some electronics which switch on when the temperature drops below 10C and off again when it rises above 12C. I switched that on a couple of days ago as yesterday saw the first frost of Autumn followed by another this morning :
There are a couple of Lithops with white flowers trying to bloom. I just hope we get enough Sunlight to encourage them to open. To give an idea of size - the Lithops plants are in 2inch (50mm) pots.