The place of the coldframe and hotbed in the culture of plants is second in importance only to the garden itself. Managed correctly, no piece of garden equipment will yield more per dollar invested.
A coldframe and hotbed have many purposes. Although the primary function is to supply plants for early crops, long before it is possible to sow seeds outdoors, the coldframe can be kept in operation throughout most of the year as an auxiliary to the garden.
Cold Frame or Hotbed – A Marked Distinction
There is a marked distinction between a cold frame and a hotbed. The coldframe is a frame-like structure, usually made of wood or metal, set on top of, or enclosing a small area, of prepared soil.
The roof, or top, is of glass sash through which the sun supplies light and heat. When this same structure is supplied with artificial heat, in addition to the sun’s heat, it becomes a hotbed.
Controlled by a thermostat allows any desired temperature to be used for heating. Thus the same structure can function as a hotbed early in the season and a coldframe later on when the heating element is turned off.
Below is a video on making a cold frame along with some good tips…