Three rivers meet in Norwich — the Yantic, the Shetucket and the Quinebaug coming together to begin the Thames — and the town rises off the water in terraces of brick and clapboard. American Landscape and Lawn Science LLC maintains the lawns on those terraces: the small level yards behind the mill streets, the wider ones out toward the reservoirs and farm roads. Riverside ground stays damp and grows hard in June, while the hilltops dry out and want overseeding by September. Edging along old granite curbs and worn stone steps is slow, particular work, and it is what makes a yard read as finished. By the time the tools are loaded, the clippings are off the sidewalk and the lawn holds a border you could have drawn with a ruler.