If your not in a big hurry and do NOT want to damage the surface.
Use either "Wet and Forget" or "Spray and Forget". Both are competitors and their product is almost identical.
It takes a few months for any stains to disappear.
www.wetandforget.com or
www.sprayandforget.com
The was a time when this kind of product was commercial only and was used to treat Public Schools and other Public and Commercial Buildings.
Now you can get one or both of these treatments in hardware stores, lumberyards and home improvement centers.
I would say the minimum expectation for 90% to 100% results is at least 2 months and at 6 months after initial application if you took any "before" pictures it would now be time to take the "after" pictures.
As a commercial contractor I use either of these products on delicate surfaces such as Synthetic Stucco (which a pressure washer will ruin) old composition roofs (which again a pressure washer will take the ceramic granules off) and other soft or worn surfaces.
ANYTHING outside that is dirty or stained from trees, bushes, mildew, mold etc. both of these products do an excellent job.
AGAIN MY ONLY COMPLAINT IS THAT THE PRODUCT DOES NOT WORK "INSTANTLY". That being said if you remove the offending tree or plant life the stains do not return. If you do not remove any plant life then you can treat 1 time per year and the stains will stay gone.
For live plants you spray them with water before applying either product, then spray again immediately after treatment and no harm will come to those plants. Everything else not hosed off including mold and mildew will die.
Only apply on dry days so that the product can chemically "bond" with the surface.
DO NOT WASH OR SCRUB after application.
And now you know ...
T.I.M.
