The message
from Mike contains these words:

The plants look look fine at present and normally I leave them alone
to face the Winter and look none the worse in the following Spring.


There are some fine Rhody specimens growing on the foothills of Scottish
mountains. These take the full force of our winter and still look good
in Springtime. Not absolutely sure but I think they are more prone to
wind damage than cold temperatures.

One could experiment by covering some plants and leaving others exposed.

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Cheers,

Compo.