Humidity does its slow work on everything in Columbia County — a driveway goes gray-green, brick picks up a film, the north side of a house darkens a shade every year. Po Boy Lawn Care and Pressure Washing takes both halves of that problem: the grass cut and edged, and the concrete, siding and walkways washed back to their own color. There is a plain pleasure in watching a wand stripe a driveway clean in a single pass. Around that runs the regular route — mowing, trimming, blowing off the hard surfaces before pulling out. A Harlem yard looks its best when the lawn and the house it belongs to finally match.