The polytunnel of dreams had a baby! A mini polytunnel – or as I saw on Instagram (that fount of all knowledge) a greenhouse in a greenhouse!
I wanted to make a space to propagate seeds and to grow-on temperature-sensitive seedlings until they were strong enough and the weather was warm enough for them to be planted in the polytunnel – so we built this propagator/seedling house.
Most of it was made from recycled, useful stuff we had lying around – yay for hoarding – but we did have to buy the soil heating cable, a thermostat (although that could be optional I guess), some capillary matting (again this is optional) and we had to get electricity into the polytunnel.
So you need some board for the base, some two by four lengths of wood, heating cable, plastic, sand and some hoops – you could use lengths of water pipe for this, I use these to make hoops for protecting vegetables on my hugelkultur.
So first make sure you have power to wherever you are setting up your baby polytunnel. We need ours to be waterproof as we have irrigation in the polytunnel.
Decide how big you will make the propagator
Make your box
We lined it with black plastic we had bought to use as weedblock – this stage might not be necessary.
Add in about 1-2 inches of sand
Our box is about 8 foot by 4 foot more or less. I had bought an 80 foot soil cable – this was more than enough.
Lay out the cable. I had to tack it in place to stop it springing back. The cable mustn’t touch itself.
Cover with another layer of sand – about 1-2 inches.
Temperature control is added – I have set mine to 17-18 degrees I think – although it does say 20 here.
To keep the heat in and to ensure that night-time temperatures don’t get too low I then built a cloche-type thing on top. I used an old frame from a mini polytunnel I bought years ago when we first moved here – before I realised that water pipe is cheaper and works just as well for constructing tunnels.
I then taped together some bits of old plastic I had made James save from when we built the polytunnel and made a new cover.
I have put capillary matting down on top of the sand with one end in a tub of water. This will ensure that the seedlings get enough water and the sand doesn’t dry out – you apparently don’t want the sand to dry out – I don’t know why.
I then left my polytunnel temperature gauge that records highs and lows in the new baby polytunnel to see what the lows would be.
Fifteen or so degrees centigrade is not bad. The temperature does get a lot higher than 17.5 degrees but I took this photo early in the morning. I am having to watch the temperature in the polytunnel as at mid-day on a sunny day it hits the 30s so I have started opening the doors a little.
So there is it – my greenhouse in a greenhouse. This weekend I will move my seedlings over and see how they do.
But first I have to plant a thousand strawberry plants – don’t even ask – this is a whole other story ……
N.B. As I now have water and electricity in my polytunnel it is highly likely I will move in permanently!