Climb away from the Ossining waterfront and the road doesn't stop rising for a while — terraced yards, retaining walls, hedges holding the line where the ground wants to leave. Green Hills Landscaping & Masonry lives on that pitch, mowing and trimming the tiers, shaping hedges, mulching beds that sit above eye level from the street. Late May is the best of it, when everything is growing at once and one afternoon's work changes the whole face of a house. Come January the trucks are out plowing the same steep drives and salting the turns where a car would otherwise slide. Ossining's hills and the towns spread around them are the territory.