With the cold snap we had this winter I’m thinking (far ahead ) about how to keep our trees from getting killed/damaged. I see soil warming cables advertised to help speed germination…but would they also help with keeping container trees a tad happier in the harsher periods of winter? I just thought it was odd that I haven’t seen a single mention of anyone using them for that purpose, so figured there must be a reason?
Soil warming cables and other sources of heat are usually used with some other forms of protection, like cloches , greenhouses, and fleece covers. Without something to hold the heat in, the cables will only warm the roots and won't provide useful heat to above ground parts of a plant, especially when strong outflow winds are present.
I would recommend you have a layer of sand on top of your polystyrene sheet first before you lay the cable, then cover with more sand. I have used cables and the "Parasene200" rod thermostat successfully for many years on such heated beds. Yes, keep the sand damp!
