Short Hills sits up on the first Watchung ridge under a canopy of old oaks, and everything that happens to a lawn there happens in shade and on a slant. Benjamin Lawn Care Company LLC works those grounds — mowing the long green aprons between stone walls, edging the curving drives, keeping turf even where the ground never quite lies flat. Winter on the ridge means an inch more than the valley below and a plow route that begins well before the first train pulls out of Millburn. To have a driveway open and salted while the sky is still blue-black is the whole argument for getting up that early. Then April comes, the dogwoods light up, and the mowers start again.