One of our readers phoned in enquiring about a black moss problem he has in KwaZulu Natal. He also kindly sent pics of the offending moss.
After gathering together all the information, answers to enquiries we made and solutions we received this is what we found out:
Constant use of high pressure hoses on walls, cement, concrete or paintwork can damage the surface and underlying cement and concrete and also be very expensive. It is far more appropriate to first try and use surface biocides which will kill the existing growth and also aid in the prevention of future growth.
Apply a solution of 1 part of sodium hypochlorite (laundry bleach contains 5% sodium hypochlorite which is adequate) mixed with 8 parts of water. Apply enough to completely saturate the black moss and leave for about a week. (Note that if it rains within 24 hours you will need to reapply the solution.) Scrub or brush off the dead moss. This treatment should keep the wall free of new growth for a while.
Gardening centres or nurseries should also be able to provide you with a suitable solution to remove the moss. These solutions normally contain ammonium sulfamate and you will need to follow the manufacturer’s instructions. (Always wear gloves when working with chemicals.)
It is best to do this in the drier months so that the wall can dry out before applying a sealer that can provide some fungicidal action against future moss growth. Speak to your friendly hardware store about suitable sealers.
You could also make a sealer using approximately 200 gm of magnesium fluosilicate crystals in about 5 litres of water which you can paint on when the wall is dry to prevent regrowth.
There are also paints available to apply that will inhibit future growth.
Moss and other vegetable and plant growth usually appears on walls that are not exposed to enough sunlight and are constantly damp.
It is important to remember when working with chemicals that you must:-
Always follow the manufacturer’s instructions.
Wear gloves and protective gear including safety glasses.
Avoid contaminating the surrounding vegetation or water.
As a matter of interest, while I was doing this research, I came across all kinds of wonderful finds about mosses. You might want to take a look at this site just for the sheer beauty of the images – and – do you know – there are people who actually cultivate mosses, there are whole communities of folk who take the most incredible photographs – someone even told me that there is a graveyard (can’t remember where) where the old gravestones are so covered in lichens and mosses that the quality of air there is absolutely incredible, so it seems mosses have lots of uses as well like for smoking malt in the production of Scotch whiskey!
And what looks more beautiful or romantic than an old stone church with lichens and moss clinging to it. OK, let me get my camera out – I need to take some photographs.
However, back to our reader’s problem, if you have had this problem or know of someone who has successfully treated black moss, please write in with your treatments and remedies.