Over a decade ago I wanted to know what temperatures my roses were feeling in winter. Max min thermometers (plastic, poorly made) were my answer. I found that temperatures at the bottom of our hill were five degrees colder than up near the house. I found that roses showing lots of mosaic virus patterns on their leaves were damaged at 28F and stronger HTs weren't.

Yeah technology. We've turned part of our passive solar collecting porch into a greenhouse and (having lost a bunch of plants there last year without upgrading the space (making it more windproof) I wanted to start to understand the temperatures.

Oh, how advanced the max min thermometers have become. Made by Thermometer World in Cumbria UK this is what I'm using.

Digital max min thermometer

I like it so much I just got a second one for plants growing in another window.

I look forward to doing what it will take to protect some of my more tender potted plants (and maybe next year make one more attempt at growing Susan Louise where I know she won't be frosted or frozen.