I've aquired a large thick clear plastic sheet from work (rescued from a bin) that I think will be good for making a cloche.
If I lay it on top of the soil, weighted at the corners, will it help to warm the soil? Or do I need it to be raised so there's an air pocket to warm up?
Lay it straight on to warm the soil. That will be fine.
If sowing anything under it I would raise it a bit and watch out as the sun warms up in spring as it could cook anything in there on a warm sunny day.
Jerry
Jerry, would cloudy plastic sheeting be a better option to maybe shield the heat? The reason I ask is that I noticed "Wickes" DIY sell quite large tough sheets for around a fiver. 8)
Using clear plastic can heat the ground enough, if there is sunshine of course and of sufficent duration, to possibly kill weed seeds, pest eggs and fungal spores (as with a sterile seed bed). It is unlikely cloudy plastic will allow enough light in to do this. Incidentally Aqui, you are actually heating the air in the soil, to begin with. This is why you do not need to leave an air layer directly under the plastic. This warm air will then pass on it's accumulated heat to the soil.
Thanks Jerry and John. I'd forgotten about air in the soil John! ::)
You can make a cloche by cutting the plastic in a semi circle.
For example, cut a 2 foot diameter for a 2 foot tall cloches.
And cut a small semi circle at the center.
Then fold the plastic and attach the sides together with plastic connectors.
This will give you a cone shaped cloche with a hole at the top.