>>>Not that surprising, as they used to heat the cold frames with manure, placed at the bottom, and soil over it.<<<
Yep, horse manure works really well for it...
I have grown salad fixins all winter by digging a trench and filling it with horse manure, covered with about 6” of soil, then put bales of straw all around that with plastic covering the top and outside of the bales, then a double plastic frame cover on top that we had to open on warmer days. Works great!
Yep, horse manure works really well for it...<<<
Yes, it does, I used it and planned to grow New Zealand Spinach over winter, it grew so well that it took over the entire bed and self sowed for several years, this was in an attached greenhouse.
It was nice, having fresh greens in the dead of winter.
There are many of the old ways, that I need to look up and see if they are still known today.
I have also used the straw bales for growing and as a quick shelter for baby chicks and ducks, drop a light bulb in the middle so they can keep warm and cover them with chicken wire and plywood, works very well.