Why connect expensive power sources when the cold frame can be heated using natural means? With an electricity-free natural heater, you can create a pleasant microclimate in the cold frame when it is still far too cold in the garden for planting. This guide explains how to do it.
How can I heat my cold frame naturally?
To heat a cold frame without electricity, you can dig a 50 cm deep pit in autumn, cover it with vole wire, leaves and straw and fill it with manure and a soil-compost mixture in February. The natural heat from the decomposition process lasts up to a year.
The starting signal is given in autumn – tips for preparation
Since the powerless cold frame heater involves digging work, preparations should be made in the fall. Thanks to this caution, you will be spared strenuous shoveling in frozen ground during the spring. How to do it right:
- Dig a 50 cm deep pit in a sunny location
- Mix one third of the excavated material with compost and store until spring
- Cover the bottom of the pit with vole wire
- Spread a 5 to 10 cm thick layer of leaves and straw on top
You can place the self-built or purchased cold frame box (€79.00 on Amazon) over the pit until next spring or cover the deep hole with sturdy wooden planks.
This is how the cold frame gets its natural heating - instructions for filling
When the lighting conditions improve in February, the first seeds can be sown in the cold frame. To create the required germination temperature of 18 to 22 degrees Celsius, fill the prepared pit like this:
- Pour fresh horse or cow manure onto the leaves and straw layer up to a height of 20 cm
- Spray too dry manure with nettle manure
- Mix too wet manure with leaves and straw
- Shovel the mixture of soil and compost over the manure in a 20 cm thick layer
Close the cold frame and let busy microorganisms do the work. Within 8 to 10 days, the decomposition process releases a natural heat that benefits seeds, seedlings and young plants. This heater serves its purpose for a period of one year. Therefore, refresh the filling every spring to heat up your plants in the cold frame naturally from February onwards.
Tip
If spring comes with bitter frost, the heat output of the natural heating system may not be sufficient. If your cold frame is a construction made of fireproof double-wall panels, simply place a flickering grave light or tea light inside as an additional heating source.
