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Hot Composting

Hot Composting

Hot Composting

Image – No Dig guru, Charles Dowding’s hotbed, copyright Charles Dowding

The Egyptians were using manure fuelled hot beds to incubate eggs as well as growing plants, thousands of years ago. In the First Century AD, Roman Emperor Tiberius grew cucumbers in wheeled hotbeds with translucent panes, that could be moved outside when temperatures were right.

Mad Emperor, Tiberius Caesar 42BC to 37AD

The Moors of Southern Europe grew seedlings in small boxes filled with donkey manure. By the Dark Ages this practice had spread to the monastery gardens of Britain. The height of the hotbed really began in the 18th century in Britain, with the need to care for new seeds and cuttings that flooded in from the New World.

Image – Deer Park’s Victorian Pineapple hot house, copyright

During the Victorian era whole sections of walled gardens were hotbeds dedicated to supplying a variety of out of season vegetables for wealthy landowners.

A manure powered hot composting bed will supply consistent warmth for two months, and will then supply a rich, moist bed for cucumbers, melons, squash and courgettes for the rest of the summer. A hotbed is the perfect ecological solution for creating a warm bed for tender plants.

Hot compost heap with wire mesh and wooden supports – image

The trick is maintaining a steady supply of heat over a long period. Manure on its own will burn out in a couple of weeks, but if you mix in equal amounts of straw, the release of stored energy will last for two months.

The hot compost bed can be created above or below ground, and is best in a sheltered spot, or inside a greenhouse. It can be a free standing heap, or contained inside a box. If you make a heap, cover the sloping edges with upturned grass turves to help retain moisture which can be lost around the edges whilst they erode. On top of the heap place a lid made out of old window panes. When mixing the straw and manure make sure that air gets into it as you turn it, and sprinkle with water. Leave it to ferment for three days.

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On the third day turn the mix, getting as much air into it as possible. Make sure it is evenly mixed, and leave to ferment for another three days. Turn it again on the six day, leave it for another three, and then on the ninth day, turn it and leave it in its final place. If in a framed box the minimum size should be 60cm high x 60cm wide x 90cm long. The pile should be firm but not compacted.

Leave the compost for at least four days, which will allow it to cool slightly. If you use it too soon, the high temperatures will damage the soil and any plants. A good test is putting a stick into the pile. The compost is ready when you can hold the warm stick comfortably in your hand.

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Once you’ve planted it up, put your plants to bed each night by laying sacking across the top to stop the heat from escaping. By day you can regulate the temperature by opening and closing the glass lid, like you would a cold frame or greenhouse.

You can start off seed trays on top of the hotbed – image copyright Charles Dowding

Many flowers and vegetable seeds love a bit of warmth to get them going (Peppers, Tomatoes, and the Gourd family), but lettuce, carrots, geraniums and delphiniums will not germinate in soil that is too warm.

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It’s such a good idea to use a hotbed if you can in your garden. It offers some control over the weather and extends the range of vegetables, fruit and flowers that you can grow. Enjoy!