On Fri, 9 Jan 2004 12:56:15 -0000, "RichardS" noaccess@invalid
wrote:

"Neil Jones" wrote in message
om...
Andy Hall wrote in message
...

That's no real issue and can easily be removed. I quite like to see
a certain amount of lichens on roof tiles. It makes them look more
interesting.....


Apparently lichens only grow in places of low atmospheric pollution,
so it's a good indicator of air quality, as well as any aesthetic
benefit.

but is the same true about moss? In fact, are moss and lichen synonymous?
I know that lichens are rarer than they once were.

I'm sitting working looking at the roof of the house opposite, and this is
liberally covered in mosses. This is sunny Twickenham, not that far out of
London and close to the Heathrow flightpaths and one of London's arterial
road, so whereas this might not be an area particularly high in atmospheric
pollution it certainly isn't the cleanest environment.

I've taken the liberty of crossposting this to uk.rec.gardning, in the hope
that one of their knowledgeable netizens may be able to throw some light on
the question.

I just discussed with SWMBO, who is a zoology graduate, but has also
studied plant life extensively.

There are a whole spectrum of lichens and some will grow in moderately
polluted conditions. Others are more sensitive to conditions, so for
example you will see a richer set of lichens in a forest in Wales than
you will in town.

They are a composite organism from a fungus and algae, bacteria or
both.

http://www.lichen.com/biology.html

Mosses are rather different, in that theyare plants and produce
chlorophyll themselves and are generally attracted to places where
there is moisture - hence finding them in gutters...

Clearly it makes sense to remove moss from gutters to avoid them
cloggin and water running down the walls, but there is no reason to
remove them or lichens from roofs. Arguably there is more risk of
damage from blasting with a pressure washer or from use of chemicals.




..andy

To email, substitute .nospam with .gl