Pine Banks holds its old oaks along the Malden line, and in July the light under them comes down in coins. Double Tree Landscaping keeps the lawns in the neighborhoods around it cut and clean, mowing on schedule, edging walks and driveways, trimming the awkward corners where a mower cannot turn. Shade lawns and sun lawns want different cutting heights, and a route that knows the difference leaves better grass behind it. Twice a year the work becomes cleanups: beds opened up in spring, leaves cleared out in fall. What remains is a yard that looks calm, which is harder to achieve than it sounds.