The Wailuku Drive side of the house has for many years been planted in hapu'u (tree ferns). When I first started working on the house (in 2006) the walls were completely covered with mold and mildew, because the sun never struck them. Over the years I've thinned out the hapu'u and removed all the other plants and fixed up a drainage ditch. The walls have stayed mostly mildew and mold free.
There's a kind of moss that likes hapu'u and likes to grow on exposed roots, and on rocks. That's what you're seeing here, along with part of the drainage ditch. I made another moss-ditch shot this morning that I really liked. In the end I chose this one.
My camera so completely nailed the exposure that I made no adjustments at all in Lightroom (also true for the ancillary image).