The Bass River carries the tide in and out behind Beverly's back yards, and in May the marsh grass greens up a full week before the lawns do. Currier Landscaping works that stretch of the calendar hard, mowing, trimming, edging and cleaning up the winter's litter so the turf gets its head start. Salt air and sandy ground make their own demands here, and a lawn near the water grows in patches unless somebody is paying attention to it. Watching a ragged spring yard come back tight and level over three or four cuts is the part of the work worth showing up for. By June the edges are crisp against the walkways and the whole property sits square to the street again.