Picking greens on a very cold day

This winter I have been doing an experiment here at the farm.. I am growing greens in an unheated greenhouse with minimal protection. Up to this point it has certainly been a fairly cold winter but not so cold that I was not expecting to pick greens from this greenhouse. Just this past week though old man winter certainly shared with us some of his piss and vinegar. Night time lows ranged as low as -10 which is not very conducive to many living things. However to my surprise these greens took it fairly well. I will say that the arugula did suffer perhaps terminal damage, but all of the others including some of the lettuce did quite well.. albeit a bit of damage but I was able to pick quite a lot of greens for a cold winters day. How is this possible you ask? Well I'll tell you. The greenhouse is protected with one layer of plastic, which gives about 7 degrees of frost protection and the lettuces etc are protected with one layer of reemay which is a fabric row cover and that provides about 6 degrees opf protection. I think the success is due to the fact that these greens have been living in these cold conditions since November. There have been weeks at a time where they have been frozen solid and I was not going to get anything from them.... The insulation from as much as three feet of snow banked up on the side of the greenhouse possibly gives an extra 5-10 degrees of protection. Meanwhile when the sun comes out and is uninhibited by a clud cover the greenhouse can get as warm as 65 degrees. Its pretty amazing to walk from ten degree winter weather into even 45 degree early spring weather with greens sprouting out of the ground. Unfortunately the rate of growth is quite slow without the use of supplemental heat, but it is amazing to me that with a bit of protection I can eat greens out of my greenhouse right now. Luckily I also have a commercial greenhouse at my disposal that allows me to cut as much as 60 pounds of greens per week.. I do however heat it when it gets below forty degrees in there.I love the fact that I can do this, and the best news here is not just for me, but so can you.