When it is cool and freezing fog develops, rime ice is formed. The rime ice forms on the sides of trees where the wind blows.
There is hard and soft rime ice.
Hard rime ice happens when the water drops in the freezing fog settle on the surface of objects. It looks somewhat clear. This is the kind of rime ice that forms on the wings of airplanes. It clings to surfaces and can be hard to remove.
Soft rime ice looks different in that it is frosty looking instead of icy looking. Usually it is spiky. You can break it off easily.
There is an explanation of the different ways rime ice forms and I couldn’t understand a word of it. You are on your own.
The pictures are from Wikimedia Commons. Except for one.
This is freezing fog in Winnipeg, Canada by, T. Tumkin, English Wikipedia.