"Richard Downing" wrote in message
...
wrote:
Runs of copper along roof ridges. Copper salts formed with rain water.
Washes down over moss. Moss either dies or doesn't start growing there.
No idea what salt is formed or why moss doesn't like that particular
salt.

Copper Sulphate probably. Rain water was a very weak sulphuric acid due
to volcanic dust, and now more significantly, a stronger acid due to
industrial pollution.

If it's legal, you could probably do the same job by spraying with weak
Copper Sulphate once a year. Magnesium Sulphate (same effect) is what
does the job in lawn moss killer, or used to before grandma got elected.

Eh? Magnesium sulphate is Epsom Salts, you can buy it at any chemist and
probably some supermarkets.

Mary

R.