Nockamixon Township runs along the Delaware, where River Road follows the water past the old canal and the cliffs stand up dark above the far bank. In May the whole valley greens at once, and Slate's Lawn Maintenance begins the season's rounds — mowing on a regular cycle, trimming the edges a mower cannot reach, cutting a clean line along drives and walks, and clearing the cuttings once the pass is finished. Upper Bucks County offers every kind of yard: riverside flats, wooded lots up the hillside, wide lawns around stone houses set back from the road. Each wants a different route and a different week. What does not change is the look of a lawn on a bright afternoon after the last pass — even, sharp at its borders, the sort of thing a person notices on the way up the drive.