moisture
shade
organic material such as dust or pollen
North-facing walls, areas behind shrubs, and siding located beneath gutters are especially vulnerable.
Once algae becomes established, rain and humidity can help it spread across larger sections of the wall.
Biological Sciences
The Easy Cleaning Method
The main trick is surprisingly simple: let the cleaning solution sit long enough to loosen the algae before you rinse
it away.
You will need:
warm water
an exterior siding cleaner or oxygen-based bleach cleaner labeled as suitable for your siding
a garden sprayer or
