The basic purpose of a hotbed is to grow vegetables when outside temperatures are still too low. With hotbeds, we can extend the time of vegetable production.
Hotbeds can be made in several ways. The most simple is to produce a tunnel out of polyethylene or polypropylene foil. Place plastic or wooden frame over vegetable bed and foil over it which should be secured with rocks, bricks or wedges. Vegetable bed will be suitable for planting when temperatures do not drop much below freezing at nights and are over 7 degrees Celsius through day. Foil can be removed when there is no more risk of frost.
Hotbed's frame can be made from wooden planks, concrete, plastic or other material. It should be about 50 cm high at the rear and about 35 cm at the front. Different heights ensure better sun rays collection and therefore higher temperatures. On the top are one or two glass elements that can be opened. Instead of glass we can use plastic windows. We can place the frame directly on the soil surface, but it is better to remove about 50 cm of soil and place protective metal net to prevent animals to enter hotbed from deep soil.
If we have enough space in the garden, we can build greenhouse. Greenhouse will extend vegetable growth even further in the winter as we can install heating elements and artificial lights.