As I looked at Craigendarroch (Hill of The Oaks) behind our house, I visualised a picture forming of a full frame of oak trees. There are other types of trees on this hill, but there's a swathe of old oaks there and in winter they have an interesting look and colour as they are covered in lichen.
My first thought was "frost covered trees". I do love the way you present Scotland to us! It's one of the countries I may never get to visit, but you bring the beauty, the rugged countryside and the wonderful vocabulary to us, up close and personal (for knowing you!)
Hard to get the perspective & size of these oak trees & I'm sure they are much bigger than they look here. They just look completely like low lying lichen …….how the eye deceives!