The Hackensack River bends slow past River Edge, and the old sycamores along it throw enough shade to change how a lawn grows from one side of a yard to the other. Diamond Landscaping & Design mows and maintains those properties — cutting, edging along the walks, trimming the fence lines, and the seasonal cleanups a river town's trees insist on. June here is deep green and humid, the grass thick, the mowing weekly and unmissable. Getting a shaded yard and a sunny one to read as one continuous lawn is the quiet trick of the job. When it works, the whole property looks like a single even stretch of green.