Hi John, i did not monitorized the temp. inside the cage at my customer location, but i can tell you that at my home with the same protection, my Butia (who s lost all leaves after seeing a -9c last november) did not see temp. below -5c. when it was -23c outside. But i think the burn leaves that my Sabal palmetto had is du to the arbotex, i did nt cover the top off the leaves.
Almost all my palms had arbotex covering all the leaves, like that, the humidity du to the transpiration when it get to hot inside(more than +15c) is absorbed by the arbotex. So that help leaves. With that technique, i almost not have burn tip. I tried some without arbotex, and i had good result too. The arbotex is just a help in case it get to warm inside.
One thing is to do not forget to put some heat at the base of the palm in the box. For better result, we need to have almost the same temp. at the base and at the top of the palm. I tried to put only light at the middle of the trunk and my soil still frozen. Even if the temp. at the middle of the box indicated +8c. The bottom was at-1c. Big difference.
So i putted 1 12 foot heat cable at the base and 1x23watts fluocompact light at the middle of the trunk, and the temp. was almost the same everywhere in the box (1-2c difference, not more). Thats for a box of 8 feets tall, 2 feets wide, 2 inch styrofoam thats it.....temp. never go down under -4c even at -20c outside.

Hope that will help you guys....

Ben

Ok, Mike, no problem with that...we will put palm trees everywhere in southern Quebec. What do you think about a Ste-Catherine or a Blv.Labelle with 2 rank of palm trees just like in Santa-Monica.

HA

Ben