Morning fog burns off the Neponset by nine, and Dorchester's yards come up warm and damp and ready to cut. Forbes Lawn Services works that window — mowing, string trimming, edging the concrete so the grass stops in a straight bright line. Spring opens with a cleanup, hauling off the grit and broken branches the cold months leave in the corners. Summer settles into a weekly cadence; autumn is leaves, again and again, until the lawn is clear. There is pride in pulling away from a Boston triple-decker and seeing every blade lying the same direction.