Lichens are either crustose (crusty), foliose (leafy) or fruticose (shrubby). This is a fine example of a shrubby lichen on hazel alongside our neighbours’ track.
A lichen is a composite organism that arises from algae and/or bacteria living among filaments of a fungus in a symbiotic relationship. The combined life form “has properties that are very different from the properties of its component organisms”. The description sounds futuristic but lichens are amongst the oldest living species.
Shrubby lichens are a good indicator of clean air. Other lichens are more tolerant of pollution.