horse manure is considered the best "heating material" for the coldframe, because the breakdown of the manure creates heat through bacteria. This warmth helps to grow vegetables early in the year. Horse manure is available as a pack in any nursery or in the garden wholesaler.
1. Dig out and cover the pit
But first a 50 cm deep pit has to be dug. The cold frame should have a glass cover facing south to take advantage of the heat. If the front of the bed is slightly lower, the bed is heated even when the sun is low. To ensure that no voles are up to mischief in the bed, it is important to stretch a fine wire mesh on the ground and the sides.
2. Fill the cold frame with straw and horse manure
The bed is now filled with straw about 10 centimeters high, which must then be treaded. This is followed by a 30 centimeter layer of horse manure. This should also be stamped together so that the remaining 20 centimeters of compost can fit on it.
Fermentation of the horse manure creates a temperature of around 15 to 20 degrees; the best temperature to plant vegetables. However, you first have to wait a week for the small biotope to have sufficient heat.