Frost arrives early on the Petersham common — white across the grass in front of the white clapboard on mornings when the rest of the county is still soft and green. Roland Barnes Gardening works with that short, brilliant hill season, mowing lawns up on the ridge and down toward the East Branch of the Swift River. Cuts stay regular right through the growing months, with edges trimmed along walks, walls and bed lines so the shape of a yard stays legible. Spring cleanups lift the winter mat off the turf; in fall the leaves are gathered and carried away before the cold locks them in place. A lawn kept this way in a town this old looks as though it has always been there.