Building A Hot Bed

So what is a hot bed?  A hot bed is a warmed, protected environment, created by heat generated from decomposing organic matter.  It is used for producing early crops in cold climates, when soil temperatures during winter are too low for seed germination.  Using hot beds to increase soil temperature through the cold winter months is a traditional technique and one of the practices used by French market gardens in their intensive polyculture.

In our cold climate region where winter soil temps are currently around 5℃ and do not warm up until September, I thought it would be interesting to experiment with this technique.  While we do use a lot of seedlings in our garden there are a number of crops where growing from seed is essential.

One of the crops we find challenging is shelling peas. Autumn plantings, generally the standard time to plant peas, are unsuccessful due to our long harsh frost season. Springs plantings when the soil temperature is warm enough for good germination (late September) results in plant maturity in early summer when very warm temperatures impact on crop productivity.  For best crop production outcomes a winter planting is necessary, but as already stated, low soil temps at this time have a significant impact on seed germination.

The process of building a hot bed is somewhat similar to building a no dig garden.  Although the main material in a hot bed is stable manure and as with a no dig garden it is finished with a layer of soil.  Unlike a no dig garden there are minimum size requirements to ensure adequate heat generation.  To maintain the generated heat cold frames, cloches or other frost protection materials are used.  I have topped our hot bed with insulnet. 

Soil temperatures are averaging around 14℃ in the hot bed.  We have planted lots of seeds so will give you an update on germination times as we go.  Lets hope all the work pays off.

I will be producing a mini guide with all the details for building a hot bed in the near future.