South Berwick sits where the Salmon Falls River slides between Maine and New Hampshire, a village of old clapboard houses that Sarah Orne Jewett once called home. LND Landscapes keeps lawns in trim here, mowing and gathering up the leaves that the big oaks and maples let go each autumn. September is a golden month in town, when the light slants low through Vaughan Woods and the grass makes one last push before the cold. Mown short beneath that light, a yard with its border running true against the stone walk has a kind of storybook calm. It is the sort of yard that makes a passerby slow down on the way to the river.