Heating the polytunnel

No sooner is our new polytunnel fully built than we have to face the next challenge; heating it.  Our requirements are to just keep it above  freezing (preferably 5 degrees C) as all the plants are perennials. The aim is to keep a balance between enough warmth to encourage speedy growth and not too much so that they grow 'soft'.  A lot of our plants will have to live a harsh life in field margins or wildlife corners so growing them hard will increase thier resilience.

We will only use about 25% of the space this year so there is no point heating the lot. So, you will see that I have put up a bubble-wrap tent within the tunnel to reduce the area.  Another challenge is that we

have no electricity yet so I have chosen a basic propane convetor heater that does not have any electrical controls of fans; just a basic pilot light and thermastat.

In theory this heater is meant to be plenty 'man' enough for the job but so far the tented area is not noticably warmer than the rest of the tunnel unless I have it up full - in which case it guzzles the gas.

It appears that the tunnel is consistantly between 4 and 8 degrees warmer than outside. But....unfortunately when its -11 degrees, that still meant my poor little plants where temporarily at minus 3. Oh dear. Well they seem fine so hopefully they won't go too dormant.