In article ,
Janet writes:
In article o.uk,
says...

Nice house wall painting weather, patching up the few places the
paint has failed. One patch I *know* I wire brushed and repainted
last year. It's failed again, because there must be moss embeded into
the stone/old lime mortar.

So how to kill the blasted stuff, preferably in one hit and
permenantly. Will Roundup do it?

No you need a specific moss killer.

Well, Pathclear (a similar product) kills moss pretty instantly,
much faster than it kills the plants.

Doing it permanently means changing the conditions to be
unfavourable to growth, e.g. repointing and stopping gutters
overflowing down it.

Shed sells something for treating
mossy roofs or you could use ferrous oxide in water, the active
ingredient in lawn moss treatments. When it's dead brush it out of the
crevices with a wire brush.

Lawn moss killers usually have warnings against getting them on
stone/brick/paving, as they can stain permanently.

Talking of moss killer I posted a query a few weeks ago asking advice
on about dethatching the "lawn" which had become so mossy it was sodden
and unusable, grass rapidly retreating.

I borrowed an electric lawn scarifier to try, which was so
effective I went out and bought the same model (£60 in Dobbies GC, same
in B and Q). It raked out enough moss to fill 16 cubic-metre builders
bags. Then I treated the lawn with a moss, weed and feed gritty stuff.
Huge black patches where it had been pure moss.

However, weeks later the moss is all gone, the ground is not nearly
as wet and spongy and and the grass is rapidly growing back into the
gaps and looking good. Lots of work but worth it.

I found (by accident) that setting the mower one stop lower than
usual caused it to rip out tonnes of moss, a much larger volume
than the amount of grass cuttings normally collected.

I have used the combined lawn moss/broadleaf weed killers and
fertilisers in the past. They used to be very effective, but the
broadleaf killer in them is now much less effective (moss killer
still works instantly).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In message , Martin
writes
On Thu, 11 Jul 2013 08:39:53 +0100, Chris Hogg wrote:

On Wed, 10 Jul 2013 17:50:43 +0100 (BST), "Dave Liquorice"
wrote:

Nice house wall painting weather, patching up the few places the
paint has failed. One patch I *know* I wire brushed and repainted
last year. It's failed again, because there must be moss embeded into
the stone/old lime mortar.

So how to kill the blasted stuff, preferably in one hit and
permenantly. Will Roundup do it? The weather looks set fair for a day
or two so I could squirt it tomorrow and leave it for a couple of
days to get down into the roots before removing the top growth and
repainting.

Along with what the others have said, Jeyes Fluid will kill moss, but
the smell lingers for a week or two and I doubt if it's permanent.
Creosote may also work but I have no experience. As Janet was
thinking, ferrous sulphate is traditionally used to treat moss in
lawns, but this will slowly oxidise, will probably give you a brown
stain,

black!

Moss turns black (and hopefully dies), but ferrous sulphate stains
concrete etc brown.

and having oxidised may lose its effectiveness, but I don't
know about that last bit.

If you apply too much moss killer you can kill the grass as well as my
wife proved earlier this year.


Another thought, and I don't know how well it would work, comes from
the idea that if you run a strip or wire of bare copper along the
ridge of your roof, the very slow bleed of copper as it corrodes
prevents moss from growing on the roof. Perhaps you could try painting
the patch on your wall with a dilute copper sulphate solution, or a
copper-based fungicide such as Bordeaux Mixture. The latter is
unlikely to leach away in a hurry, so may remain impregnated in the
lime mortar and be a permanent solution (but not a solution, IYSWIM!).

You used to be able to buy 25kg sacks of ferrous sulphate for less than
£10, but then the EC stepped in, and declared it a hazardous substance.
[Well, it certainly is, if you drop a 25kg sack on your foot, or give
yourself a hernia lifting it in and out of the car boot.] These days,
for the ordinary man-in-the-garden, it's only available in (say) 1kg
bags, and costs around £10.
--
Ian