when to wrap my palms, yukka and tree ferns etc....

OK, I can see the reed screen cooling the Palms from the sun, but is it the opposite in winter if you think about it? It is the wet weather we have that causes most problems to tropicals not the frost. We have quite a mild winter normally. I worked in Perm, Russia and Quebec City, Canada over the years and it gets -30 for long periods, but the snow is dry and powdery, not the wet slush that we get.

 

Arh, but how many palm trees did you see.

I agree the wet is a problem, but if its very mild its not, its a combination of wet and cold at the same time.
But total continuous frost, even if dry, will normally kill most slightly tender plants.

 

As soon as I pressed Post reply I thought, wait a reed screen ain't going to stop any rain!