Power Washing and Roof Cleaning Forum

Welcome to the National Soft Wash Alliance, America's Number One Networking and Training Forum. Join Today, Donations to keep the forum going are accepted, Bottom of the Home Page
Members Login
Post Info TOPIC: Lichen Seems to Never Return? (A Good Thing)

Approved Exterior Cleaner

Status: Offline
Posts: 1215
Lichen Seems to Never Return? (A Good Thing)

I mentioned before about lichen not returning to the scene once it has been killed off from the initial cleaning.  Well,..I seen more jobs this past season that I was previously at 4-5 years ago I guess,..and the lichen is not returning,..the moss does return,..but still wondering why the lichen doesn't come back?  

Anyone else notice this strange phenomenon?



Raystown Pressure Washing

Since 1996

Approved Exterior Cleaner

Status: Offline
Posts: 2926

I have not looked Jeff. I actually never thought about it. The roofs we have gone back to are roofs I personally treated and now they are treated by one of the crews so I seldom see them. Now I will remember to put a question about lichen on their sheets.

My only guess is that lichen must take a much longer time to grow once the spores are happily eating away at the algae. Time for research.

Drum roll please... Some good information and a short read. Lichen Growth

"Like all living things lichens need nutrients and energy to grow. Nutrients they obtain from the air (including dust), water and some from the substrate they are growing on. Energy they obtain through photosynthesis, which is the role of the algal partner. They can also be incidentally fertilized by bird and insect dung."

"They grow very slowly, some species more slowly than others. Rates of growth can vary from 0.5mm per year to 500mm per year. Their slow growth rate equates with their long life."

"Lichens live all across the world, in Antarctica they can be found living just below the surface of rocks, in deserts, providing there is a permanent substrate they can be found surviving the hottest sun, they can also be found in rock pools on the sea shore and on the roofs of our buildings."




Brett Thompson

Blue Ridge Exterior Cleaning


434-466-1324    540-949-6277


Approved Exterior Cleaner

Status: Offline
Posts: 779

I frequently check back on roofs when I'm in the area (more for my own knowledge and curiosity). I have noticed:

Lichen is the most resilient of the 3. The only times I've ever had to go back and do touchups is because of lichen and it's usually the really large ones (3-4"+). The roof will be spotless w the exception of a few lichen hanging on.

Algae comes back first. Ive seen algae come back under 2 years but its generally only in areas with heavy tree growth near the house or tall mature trees.

I've seen moss come back only after many years and under Oak trees.

Cant say I've seen lichen grow back on any roof I've done.



Erik Baumer

Roof Cleaning Video

Long island roof and exterior cleaning

Long Island Cedar Shake Cleaning

Pressure Washing Long Island NY


Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.

Tweet this page Post to Digg Post to Del.icio.us
Please log in to join the chat!