Overhead tree coverage also means constant organic fall: pollen, sap, leaf debris, and fine particulate that coats exterior surfaces and feeds biological growth as it decomposes. On brick and stone homes — common in Tyrone's higher-end custom builds and developments like Trademark Quality Homes' newer communities — this results in dark streaking along mortar lines, discoloration on lower courses near the grade, and in some cases lichen growth on chimney faces and stone accents.