Hot beds have been round for a number of years introduced by Victorian gardeners to produce additional heat in the winter to produce crops such as strawberries and salad crops out of season. Hot beds us the heat created by bacteria and other soil organisms as they try to break down organic matter fuelled by nitrogen in fresh farmyard manure or fresh horse manure– horse manure being the best source.
Although it might seem strange one of the problems with hotbeds is to try to maintain an even temperature and not to allow the hot bed temperature to become to high as hotbeds can produce a significant amount of heat.
The GardenAdvice version of hotbed beds uses old brick or builders pallets cut in half to form a square raised bed. The outside walls are stuffing with straw to insulate and hold the heat in. Next into the raised bed place some straw to 150 mm deep then on top of this place 75 mm of fresh manure, its important to use fresh manure as this will contain the nitrogen in the form of urine from the animals to start the process by feeding the bacterial to generate the heat. Finally cover with 75 mm of clean weed free top soil or compost and water well.
With the hotbed constructed you can now cover with a clear plastic to create a type of cloche using wire or similar to dome the plastic cover. You will need to remove the plastic later to sow the seeds.
After a few days the hot bed will start to heated up and you can start sowing seeds or placing plants such as strawberries in pots directly into the soil on the hot bed underneath the plastic sheeting. A suitable temperature is maintained by watering and if required ventilating.
Once the hotbed has finished and been cropped it can then go on to be used as a raised bed for growing Marrows or cucumbers or if it’s in a greenhouse melons. Then after the second crop in the autumn the hot bed contents which will have rotted down can be dug into your vegetable plot to supply a valuable source of humus too improve the soil.