In article , Bob Hobden
writes

Yes, I too have it on some of my shrubs. You should consider yourself very
lucky that you have lichens in your garden, they only grow in good quality
air and have only made a slow comeback since the Clean Air Act forced people
to use other forms of heating besides coal/wood in London. Cherish it, it's
a fascinating story in itself.
http://en.wikipedia.org/wiki/Lichens




We have loads on our trees in the garden and around the area. However a
lot of people in Amersham burn wood fires, it seems to be a fashionable
thing nowadays, though they tend to bur logs for 'supplementary' heat as
opposed to us, who burn logs for main lounge heating.


--
Janet Tweedy
Amersham Gardening Association
http://www.amersham-gardening.net