One other frost related tip: I worked a few years as co-director of a CETA (federal funded jobs program) youth gardening project: we taught various organic techniques, including winter gardening where the night temperature could sometimes settle at 120* for a few hours. (A guy named Steve Tracy started the program for conventions/solar gardening as a town-based program. He recruited me when the fed program funds were available.) One feature of the program was teaching kids to build solar pods using a design a design developed buy a guy in New Hampshire.). The pod walls were constructed using two depths of 2×12 lumber with 2″ foam insulation. The foam was covered with sheet metal to retard deterioration an make things diffulct for mice looking to burrow into them for a snug winter. Steve also had gotten funding to research the efficacy of the pods for winter growing. He ran into two puzzling situations that I was able to explain, one of which I’ll treat here because it relates to this post. In freezing weather, sometimes leaf crops that were mature, essentially covering all the soil, were nipped by frost while immature plants were fine. This was the same issue as the seaweed mulch an broccoli above. Chlorphyll effeciently reflects infrared radiation, so the radiation from the soil was thwarted from protection all but the bottom leaves. Harvesting alternate mature plants would probably have been enough to save those remaining in the pod. I organized using one of our pods as a hot-bed, 6″ of soil over a foot and a half of horse manure. One of the kids set out a tomato plant in about January or February. That winter had extremely hard freezes but the plant survived until someone forgot to close the pod in may. (Even in sever cold, the pods can overheat in bright sun if not ventillated a bit.)