Mosses appear wherever conditions favor them over grasses

Evidence

What my caller was observing was that his grass was dwindling, and the mosses which had always been there were now taking advantage of the open space. Mosses cannot kill grasses. They simply haven’t the ability to outcompete them. Mosses appear in a lawn when conditions for moss growth are better than conditions for grass growth. Too much shade or water, too low a pH, soil compaction—any of these things can discourage grasses and let the mosses appear. — Robin Wall Kimmerer, Gathering Moss, 394

Categorization

• XREF: Ties to reading disturbance and land-use from present landscape — a homeowner misreads moss as cause when it is symptom of site conditions.