Hardy Tropicals UK

I drapped all the plants and thought i did wrong, but they all survived in the back garden. I think this advice is good but for my carport area (sealed) im putting carpet down under the pots to see if this brings the temperature up, as i had a few frozen pots, even thouh they were not exoposed to the elements. The CIDPs will not be drapped, but wrapped tight in fleece, and the cordylines tied up with string with no fleece.

Panama Pete wrote:I drapped all the plants and thought i did wrong, but they all survived in the back garden. I think this advice is good but for my carport area (sealed) im putting carpet down under the pots to see if this brings the temperature up, as i had a few frozen pots, even thouh they were not exoposed to the elements. The CIDPs will not be drapped, but wrapped tight in fleece, and the cordylines tied up with string with no fleece.

I think your frozen pots are extremely unlikely to have been frozen by cold coming up through the ground, and insulating the pots from the ground cuts the plants off from warmth radiating upward. I'd suggest if you have a probe thermometer to place one under a pot to monitor the temp. I would be very surprised if it was colder than the air on very cold nights.

You don't mulch plants to stop the cold ground cooling the air, you mulch to stop the cold air from freezing the ground

This topic reminds me of a Gardners World programme with Geoff Hamilton who placed a largish box in his greenhouse three quarters filled with polystyrene granules into which he placed the glass inside from a thermos flask full of hot water, leaving just an inch or two of the double insulated glass tube sticking above the polystyrene.
It would be worth a try not just for heating a cold greenhouse but could also be used for propagation.