Saturday morning in the brick-and-hedge blocks of northeast Queens has a sound to it, and part of that sound is a mower working a front lawn the size of a living room. Alexander Landscaping Corp cuts and edges those squares of grass, trims along the fence and the front walk, and shapes hedges so the sidewalk stays open. Spring starts with beds cleared and mulched; November finishes with leaves gathered before the wind moves them next door. City yards are small, which means every edge is visible from the street and not one of them can be fudged. Done well, a Queens front lawn lifts the look of the whole block, and the block notices.