caffeinated
Mame
Out of curiosity I put a few bluetooth thermometers out during our deep (for Seattle) freeze. Meter A @ 13°F was up on the bonsai bench completely exposed. (I had previously put one under an inch of substrate in a pond basket up on the bench, and it was consistently about 4 to 5 degrees warmer than completely exposed). Meter B @ 43°F was on the floor of the insulated but unheated garage. Meter C @ 30°F was in a pond basket on the ground, buried about an inch in typical APL substrate, about 3 feet lower than the bench. These measurements were from day two of the cold and the garage was pretty consistently within a degree or two of 43. I was really surprised by the difference from the bench to being on the ground.
