There is a particular green that arrives in Central Islip yards the day after a summer rain — deep, almost blue in the shade of the old street maples. Dark green Landscaping Corp works to keep it there: regular mowing, crisp edges along the driveway and the curb, trimming, beds kept weeded, and cleanups when the season turns over. The ground is flat and the blocks are long, so a lawn is seen from far off and the stripes ought to still be straight at the end of the run. Autumn drops its leaves here all at once, in a matter of days. The crew keeps coming back until the last of them is gone.