Plants on walls provides another layer of insulation, perhaps not heat, exactly, but insulation properties much like your solar blanket does @drdawg
, but of course, certainly not the very same intensity. I have a bunch of English Ivy because as you know it grows fast and can be invasive. But I am reading it should only be grown on brick or stone as it is strong enough to bring down a poly panel like on the GH. So, I guess that's out for now. The ugly Mylar panels will go up again next winter to guard against the north side cold.