Interesting thread, thanks for sharing! I would just like to add to what Leo mentioned regarding water and it's effects, for when you (or others) get to that stage. Water moves, and I've seen some abstracts of studies that show how air, nutrients as well as temperature effects are carried down through the soil. It's been a while, but I seem to recall that the more porous the soil, the greater the depths effects are seen. There were other factors influencing this, such as soil moisture saturation, and frequency and duration of precipitation. For instance, a cold, hard rain after a dry spell chills deeper. And no, I don't have a clue as to where I saw this, many years ago. If I may ask, where did you find these thermistor devices? I wonder if they could be modified so that the data could be recorded realtime. Also, if one of the devices failed you would know it, and could take action. I've been working some with the Arduino type micro controllers, and there is a vast resource base of the cleaver things that people have done with them. Dave Brastow Tumwater, Washington USA - just starting a week of sunny days, with high temps reaching the low 40's during the day, and mid-20's at night. Quite unusual for around here, and a bit rough on the emerging bulbs, but a welcome respite from the rain. P.S. Gastil,I was looking at some of your other photos; is that lovely plant you're measuring in IMG_4575 a /Libertia caerulea/?