By September the white pines above Tripp Pond throw long afternoon shade, and the grass beneath them grows slow and asks for a careful hand. Cassella Tree Service, LLC works those shaded Poland yards — mowing, trimming, edging, leaf and needle cleanup, mulch renewed around trunks and beds put in order before the cold. A lawn under big trees is its own puzzle: thin soil, root flare, a whole season's drop to move. Done right, the yard looks as if the woods simply decided to open a room in the middle. Poland, Casco, New Gloucester, Minot, Oxford and Mechanic Falls are within reach.