I am an old gardener, many years of perfecting his greenhouse. First staged in her warm bed: dug two-foot holes in the ground, put in it a layer of twigs, stems, and covered with earth, rammed. On top of sketched leaves and waste paper, a little of the soil in which earthworms let loose, and again a layer of earth.This bed was warmed itself for many years. In addition, I have in the greenhouse the plants are watered by the rain. For this I made the rays of greenhouse the roof is not out, as usual, but inside, in the middle. Turned out the chute, by which rainwater flows down in a metal barrel for watering. Under the barrel you can build a fire, to pour warmed water. Cold nights and warm barrel still heats the greenhouse. So I always have a good harvest.