The Bronx River runs quiet along the western edge of Scarsdale, and the ground tips toward it — which is why so many lawns here end in a slope and begin at a retaining wall. Mario Forgione Landscaping, Ltd. mows and edges that kind of ground, trims back whatever crowds the walk, and hauls off the debris that collects where the land falls away. In winter the same terrain gets interesting in another manner, and the work turns to plowing, shoveling and salt on driveways that pitch straight toward the road. Late spring evenings are the best of it: the mowers shut down near Ardsley Road, the air smells cut, and the lawns hold their lines into dusk. Grass season or snow season, the map is the same one — Scarsdale and the towns just over its borders.