On 2 Mar 2009, at 11:48, Jane McGary wrote: > I laid sheets of microfoam insulation . . . directly on top of the plants > and pots inside the frame . . . English gardeners who kept tender plants in frames (cyclamen, iirc) placed a single layer of newspaper over them before shutting the frames down when serious cold threatened. (Perhaps someone reading remembers the same article and can give us a reference: iirc, the glass over the frames was heavy salvaged plate glass a good fraction of an inch thick. Does that ring any bells with anyone?) And let us not forget the hobos, tramps, and bums of yore who knew that stuffing a sheet of newspaper under their outer clothing greatly improved their comfort in cold weather. It doesn't take much to give tender plants effective protection from hard frosts. The key element is that the earth itself acts as a source of heat, at the surface about 50F (not a very warm source of heat!), so if the flow of heat upwards and outwards can be retarded even a little, the temperature in a frame will go up. Following that line of reasoning leads me to believe that the size of frames is important: individually they should be as wide and long as you can afford wothout making access to the back or middle overly awkward. What are the dimensions of your frames, Jane? Mine are 48×32" boxes made of thick yellow cedar with Coroplast covers. -- Rodger Whitlock Victoria, British Columbia, Canada Maritime Zone 8, a cool Mediterranean climate on beautiful Vancouver Island http://maps.google.ca/maps/…