Tree branches touching a roof will scratch and gouge roofing materials when the branches are blown by the wind. Falling branches from overhanging trees can damage, or even puncture, shingles and other roofing materials. Leaves on a roof system’s surface retain moisture and cause rot, and leaves in the gutters block drainage. Moss can grow on moist wood shingles and shakes and algae also can grow in shaded, damp areas. Once it grows, moss or algae holds even more moisture to a roof system’s surface, causing rot and deterioration in addition to a greenish-black stain. In addition, moss roots also can work their way into a wood deck and structure. Trees and shrubs should be trimmed away from homes and buildings to eliminate damp, shaded areas, and gutters should be kept clean to ensure good drainage.