Introducing the much underrated Lichen . its everywhere! and causes no harm bless it ... those yellow patches high on roof tiles, the silver patches on trees, the gray blobs on rocks and stone walls . lichens. We have 2700 types in the UK alone.
TOP TIP it's a cachers friend - If ever muggled and asked what the dickens you are doing looking around a rock or tree or building, just tell them you are auditing Lichen colonies .. see how fast they walk away with worried stares back at you, mumbling 'Geek' as they go.
Click here for a link to a nice introduction to Lichens, If you like them then be prepared to beat yourself up mentally studying them. Nightmare to name and identify accurately.
Lichens are actually two things living as one, a fungus and a plant, one can't survive without the other. The fungus gives protection from the weather, the plant the energy from sunlight and water.
They are used to make some antibiotics and many dyes (including litmus paper dye) and were also used to stuff mummies in Egypt. Handy.
But here's where they can get fascinating ( to me at least) , the crust like ones grow really slowly, the ones you see on trees and rocks usually grow about 1mm a year, so if yo measure from the middle to the outer edge and it reads 10 cm you are looking at a 100 yr old lichen .. some are HUGE! but beware, this does not mean an old stone wall is that old, oh no, as the Lichen may well have been growing on the stone well before it was picked up and put in a wall. Graveyards are full of lichens , see how the sizes match the date on the stones. The tree here at gz has yellow lichen galore on its south west side, opposite to what people would have you believe, that being that they grow with moss on dark wet surfaces. see the 'odd' patch by its self, up above head height on the North face? strange, may need to stand on a stone to see it properly.
They do not harm trees or rocks, and in fact are often great indicators that the environment and air quality is good.
So next time you see one, I will have done my job, as before you'll likely not have bothered even seeing one!
The others in this series :
GC25MON ZC#12Somewhere over the road from the rainbow
GC25M2Q ZC#13 Finger Lichen Good
GC24VKT ZC#14 Chick or Egg?
GC25Q2B ZC#15 Tiny
GC25Q3E ZC#16 The devil and the crossroads
GC25Q3K ZC#17 Zagcattalogue
GC25Q3M ZC#18 One eyed Willy
GC25Q3Q ZC#19 The Black Rabbit of Inle