What is the dark staining on my siding? Most likely it is mold. All mold needs to grow is moisture (humidity) and a food source… and it will grow anywhere. biprincesstx2020-01-12T18:51:45-06:00January 12th, 2020|Pressure Washing FAQ| Share This Story, Choose Your Platform! FacebookTwitterLinkedInWhatsAppPinterestEmail Leave A Comment Cancel replyComment Save my name, email, and website in this browser for the next time I comment.