First I wanted to check the soil temperature.
We have had single digit temperatures twice so far this fall and winter,but the ground hasn't froze over yet.
Also 48* inside greenhouse enclosure.
As you can see I have thermostat heat tape on the trunk of queen palm and trunk of the basjoos,also Xmas mini lights up on the foliage,and oil filled radiator heater.It has never been below 32* in there,even when the temp dropped to single digits outside,I think square straw bales 5ft high have been helping keep it nice and toasty inside.
My robusta is looking good only with Xmas mini lights on the fan leaves and a rope Xmas light around her trunk.
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Here are a few more bananas,Yuzu lemon tree and palms with no heat protection,and checked them and they are still looking good as well,so if it stays on the mild side,things should sail through this winter looking good.