Great Kills Harbor holds its masts in a soft row all summer, and the yards that climb the blocks above it turn a deep, watered green by June. S&L Landscaping inc works those streets — mowing, trimming, edging, and the steady weekly rhythm that keeps a lawn even from the sidewalk to the back fence. There is a real pleasure in the last pass of an afternoon, when the stripes line up toward the water and the clippings are swept off the walk before the truck pulls out. Sea air is generous to grass down here, and it also asks for patience; the work is giving it that. By the time the light goes long over the Lower Bay, a finished yard looks like someone loves it, because someone does.