Moss and lichen
Three different organisms treated as one green problem. Where they grow tells you more about the fix than any product does.
In detail
Algae, moss and lichen are distinguished by appearance and they are not the same organism: algae is a green film, moss a soft cushion, lichen a flat crusty patch fused to the surface. A paving manufacturer's guidance treats them together for one reason that matters more than the differences — all three are prevalent where the area is heavily shaded, under trees, or not laid to an adequate fall, so the growth is reporting a drainage and light problem rather than a cleanliness one. Its practical instructions are worth having. Treatments take some days and work best in a spell of dry weather. Thick growths are scraped off first. Dead growth weathers off rather than needing removal. And two product cautions are specific: preparations containing ferrous sulphate react with concrete to leave a brown stain, and sodium hypochlorite will burn or kill plants and vegetation, so adjacent lawns and borders must be protected. Pressure washing removes the growth and the jointing material together if the lance is aimed down at the paving rather than held at a shallow angle, which is how a cleaned patio loses its joints and gains weeds the following year.
What works
Pressure washing is effective against Moss and lichen Supported
Why
- Moss and lichen is explained by Moisture control and recurrence
- Moss and lichen is explained by Surface roughness
Hacks and claims involving this
- Jet-washing the patio every spring Supported
Sources for this page
Sources
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That algae, moss and lichen are distinguished by appearance and are prevalent in heavily shaded areas, under trees or where there is inadequate fall; that treatments take days and work best in dry weather; that ferrous sulphate products react with concrete to leave a brown stain; and that sodium hypochlorite will burn or kill plants and vegetation. (states this directly)
Verification: a person has read the passage relied on.
Read on — General Advice, Power Washing, Acid Washing, Seasonal Maintenance, Sealants, the per-stain sections and Organic Growth. Supports the claim as stated.
Last reviewed by a person on .